task posting v3: moving away from ThreadTaskRunnerHandle

To continue the migration away from TaskRunnerHandles, the codebase
was refactored using the following scripts:
shell script:
https://paste.googleplex.com/4673967729147904
python:
https://paste.googleplex.com/5824001174667264

This will do a few sed-like modifications, changing calls to methods of
ThreadTaskRunnerHandle to calls to methods of
SingleThreadTaskRunner::CurrentDefaultHandle, and swapping includes.

Bug: 1026641
AX-Relnotes: n/a.
Change-Id: Ia33b6dfebb15937481c619f5c838720ce7bb2676
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4031817
Commit-Queue: Gabriel Charette <gab@chromium.org>
Reviewed-by: Gabriel Charette <gab@chromium.org>
Owners-Override: Gabriel Charette <gab@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1074085}

android_webview/browser/aw_contents.cc

@@ -60,7 +60,6 @@
 #include "base/supports_user_data.h"
 #include "base/task/single_thread_task_runner.h"
 #include "base/threading/thread_restrictions.h"
-#include "base/threading/thread_task_runner_handle.h"
 #include "components/android_autofill/browser/android_autofill_manager.h"
 #include "components/android_autofill/browser/autofill_provider_android.h"
 #include "components/autofill/content/browser/content_autofill_driver_factory.h"
@@ -1109,8 +1108,8 @@ void AwContents::SetPendingWebContentsForPopup(
     // TODO(benm): Support holding multiple pop up window requests.
     LOG(WARNING) << "Blocking popup window creation as an outstanding "
                  << "popup window is still pending.";
-    base::ThreadTaskRunnerHandle::Get()->DeleteSoon(FROM_HERE,
-                                                    pending.release());
+    base::SingleThreadTaskRunner::GetCurrentDefault()->DeleteSoon(
+        FROM_HERE, pending.release());
     return;
   }
   pending_contents_ = std::make_unique<AwContents>(std::move(pending));

android_webview/browser/aw_form_database_service.cc

@@ -8,9 +8,9 @@
 #include "base/callback_helpers.h"
 #include "base/logging.h"
 #include "base/memory/ptr_util.h"
+#include "base/task/single_thread_task_runner.h"
 #include "base/task/thread_pool.h"
 #include "base/threading/thread_restrictions.h"
-#include "base/threading/thread_task_runner_handle.h"
 #include "base/time/time.h"
 #include "components/autofill/core/browser/webdata/autofill_table.h"
 #include "components/webdata/common/webdata_constants.h"
@@ -35,7 +35,7 @@ AwFormDatabaseService::AwFormDatabaseService(const base::FilePath path)
       has_form_data_completion_(
           base::WaitableEvent::ResetPolicy::AUTOMATIC,
           base::WaitableEvent::InitialState::NOT_SIGNALED) {
-  auto ui_task_runner = base::ThreadTaskRunnerHandle::Get();
+  auto ui_task_runner = base::SingleThreadTaskRunner::GetCurrentDefault();
   // TODO(pkasting): http://crbug.com/740773 This should likely be sequenced,
   // not single-threaded; it's also possible these objects can each use their
   // own sequences instead of sharing this one.

android_webview/browser/aw_web_contents_delegate.cc

@@ -26,7 +26,6 @@
 #include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/task/single_thread_task_runner.h"
-#include "base/threading/thread_task_runner_handle.h"
 #include "components/navigation_interception/intercept_navigation_delegate.h"
 #include "content/public/browser/file_select_listener.h"
 #include "content/public/browser/permission_controller_delegate.h"
@@ -186,8 +185,8 @@ void AwWebContentsDelegate::AddNewContents(
     // window, so we're done with the WebContents now. We use
     // DeleteSoon as WebContentsImpl may call methods on |new_contents|
     // after this method returns.
-    base::ThreadTaskRunnerHandle::Get()->DeleteSoon(FROM_HERE,
-                                                    std::move(new_contents));
+    base::SingleThreadTaskRunner::GetCurrentDefault()->DeleteSoon(
+        FROM_HERE, std::move(new_contents));
   }
 
   if (was_blocked) {

android_webview/browser/gfx/browser_view_renderer_unittest.cc

@@ -16,7 +16,6 @@
 #include "base/bind.h"
 #include "base/location.h"
 #include "base/task/single_thread_task_runner.h"
-#include "base/threading/thread_task_runner_handle.h"
 #include "components/viz/common/quads/compositor_frame.h"
 #include "components/viz/common/surfaces/frame_sink_id.h"
 #include "content/public/test/test_synchronous_compositor_android.h"
@@ -359,7 +358,7 @@ RENDERING_TEST_F(CompositorNoFrameTest);
 class ClientIsVisibleOnConstructionTest : public RenderingTest {
   void SetUpTestHarness() override {
     browser_view_renderer_ = std::make_unique<BrowserViewRenderer>(
-        this, base::ThreadTaskRunnerHandle::Get());
+        this, base::SingleThreadTaskRunner::GetCurrentDefault());
   }
 
   void StartTest() override {
@@ -627,8 +626,9 @@ class RenderThreadManagerSwitchTest : public ResourceRenderingTest {
       case 1: {
         // Switch to new RTM.
         std::unique_ptr<FakeFunctor> functor(new FakeFunctor);
-        functor->Init(window_.get(), std::make_unique<RenderThreadManager>(
-                                         base::ThreadTaskRunnerHandle::Get()));
+        functor->Init(window_.get(),
+                      std::make_unique<RenderThreadManager>(
+                          base::SingleThreadTaskRunner::GetCurrentDefault()));
         browser_view_renderer_->SetCurrentCompositorFrameConsumer(
             functor->GetCompositorFrameConsumer());
         saved_functor_ = std::move(functor_);

android_webview/browser/gfx/overlay_processor_webview.cc

@@ -845,7 +845,7 @@ OverlayProcessorWebView::LockResult OverlayProcessorWebView::LockResource(
                                   weak_ptr_factory_.GetWeakPtr(), resource_id,
                                   overlay.surface_id);
   auto return_cb_on_thread = base::BindPostTask(
-      base::ThreadTaskRunnerHandle::Get(), std::move(return_cb));
+      base::SingleThreadTaskRunner::GetCurrentDefault(), std::move(return_cb));
 
   result.unlock_cb = base::ScopedClosureRunner(std::move(return_cb_on_thread));
   return result;

android_webview/browser/gfx/test/fake_window.cc

@@ -11,8 +11,8 @@
 #include "base/bind.h"
 #include "base/location.h"
 #include "base/synchronization/waitable_event.h"
+#include "base/task/single_thread_task_runner.h"
 #include "base/threading/thread.h"
-#include "base/threading/thread_task_runner_handle.h"
 #include "ui/gl/gl_bindings.h"
 #include "ui/gl/gl_utils.h"
 #include "ui/gl/init/gl_factory.h"
@@ -118,7 +118,7 @@ void FakeWindow::PostInvalidate() {
   if (on_draw_hardware_pending_)
     return;
   on_draw_hardware_pending_ = true;
-  base::ThreadTaskRunnerHandle::Get()->PostTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
       FROM_HERE, base::BindOnce(&FakeWindow::OnDrawHardware,
                                 weak_ptr_factory_.GetWeakPtr()));
 }
@@ -273,7 +273,7 @@ void FakeFunctor::ReleaseOnUIWithoutInvoke(base::OnceClosure callback) {
           &FakeFunctor::ReleaseOnRT, base::Unretained(this),
           base::BindOnce(
               base::IgnoreResult(&base::SingleThreadTaskRunner::PostTask),
-              base::ThreadTaskRunnerHandle::Get(), FROM_HERE,
+              base::SingleThreadTaskRunner::GetCurrentDefault(), FROM_HERE,
               std::move(callback))));
 }
 

android_webview/browser/gfx/test/invalidate_test.cc

@@ -269,7 +269,8 @@ class InvalidateTest
       : task_environment_(std::make_unique<base::test::TaskEnvironment>()) {
     begin_frame_source_ = std::make_unique<viz::ExternalBeginFrameSource>(this);
     root_frame_sink_proxy_ = std::make_unique<RootFrameSinkProxy>(
-        base::ThreadTaskRunnerHandle::Get(), this, begin_frame_source_.get());
+        base::SingleThreadTaskRunner::GetCurrentDefault(), this,
+        begin_frame_source_.get());
 
     root_frame_sink_proxy_->AddChildFrameSinkId(kRootClientSinkId);
 
@@ -279,7 +280,7 @@ class InvalidateTest
     // use single thread for both as we want to control timing of two threads
     // explicitly.
     render_thread_manager_ = std::make_unique<RenderThreadManager>(
-        base::ThreadTaskRunnerHandle::Get());
+        base::SingleThreadTaskRunner::GetCurrentDefault());
     surface_ = gl::init::CreateOffscreenGLSurface(gl::GetDefaultDisplayEGL(),
                                                   gfx::Size(100, 100));
     DCHECK(surface_);
@@ -381,8 +382,8 @@ class InvalidateTest
     // Client could have unsubscribed from begin frames or called invalidate
     // without BF, make sure it was propagated to UI thread.
     base::RunLoop run_loop;
-    base::ThreadTaskRunnerHandle::Get()->PostTask(FROM_HERE,
-                                                  run_loop.QuitClosure());
+    base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
+        FROM_HERE, run_loop.QuitClosure());
     run_loop.Run();
 
     if (did_invalidate_)
@@ -738,8 +739,8 @@ TEST_P(InvalidateTest, VeryLateFrame) {
   // Client could have subscribed to begin frames, make sure it was
   // propagated to UI thread.
   base::RunLoop run_loop;
-  base::ThreadTaskRunnerHandle::Get()->PostTask(FROM_HERE,
-                                                run_loop.QuitClosure());
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
+      FROM_HERE, run_loop.QuitClosure());
   run_loop.Run();
 
   for (int i = 0; i < 3; i++) {

android_webview/browser/gfx/test/rendering_test.cc

@@ -15,8 +15,8 @@
 #include "base/command_line.h"
 #include "base/location.h"
 #include "base/memory/raw_ptr.h"
+#include "base/task/single_thread_task_runner.h"
 #include "base/test/task_environment.h"
-#include "base/threading/thread_task_runner_handle.h"
 #include "components/viz/common/quads/compositor_frame.h"
 #include "components/viz/common/surfaces/frame_sink_id.h"
 #include "components/viz/test/compositor_frame_helpers.h"
@@ -51,7 +51,7 @@ class TestBrowserViewRenderer : public BrowserViewRenderer {
 
 RenderingTest::RenderingTest()
     : task_environment_(std::make_unique<base::test::TaskEnvironment>()) {
-  ui_task_runner_ = base::ThreadTaskRunnerHandle::Get();
+  ui_task_runner_ = base::SingleThreadTaskRunner::GetCurrentDefault();
   android_webview::GpuServiceWebView::GetInstance();
 }
 
@@ -69,15 +69,16 @@ void RenderingTest::SetUpTestHarness() {
   DCHECK(!browser_view_renderer_.get());
   DCHECK(!functor_.get());
   browser_view_renderer_ = std::make_unique<TestBrowserViewRenderer>(
-      this, base::ThreadTaskRunnerHandle::Get());
+      this, base::SingleThreadTaskRunner::GetCurrentDefault());
   browser_view_renderer_->SetActiveFrameSinkId(viz::FrameSinkId(1, 0));
   browser_view_renderer_->SetDipScale(1.0f);
   InitializeCompositor();
   std::unique_ptr<FakeWindow> window(
       new FakeWindow(browser_view_renderer_.get(), this, gfx::Rect(100, 100)));
   functor_ = std::make_unique<FakeFunctor>();
-  functor_->Init(window.get(), std::make_unique<RenderThreadManager>(
-                                   base::ThreadTaskRunnerHandle::Get()));
+  functor_->Init(window.get(),
+                 std::make_unique<RenderThreadManager>(
+                     base::SingleThreadTaskRunner::GetCurrentDefault()));
   browser_view_renderer_->SetCurrentCompositorFrameConsumer(
       functor_->GetCompositorFrameConsumer());
   window_ = std::move(window);

android_webview/browser/network_service/aw_proxy_config_monitor.cc

@@ -59,8 +59,8 @@ AwProxyConfigMonitor::AwProxyConfigMonitor() {
   TRACE_EVENT0("startup", "AwProxyConfigMonitor");
   proxy_config_service_android_ =
       std::make_unique<net::ProxyConfigServiceAndroid>(
-          base::ThreadTaskRunnerHandle::Get(),
-          base::ThreadTaskRunnerHandle::Get());
+          base::SingleThreadTaskRunner::GetCurrentDefault(),
+          base::SingleThreadTaskRunner::GetCurrentDefault());
   proxy_config_service_android_->set_exclude_pac_url(true);
   proxy_config_service_android_->AddObserver(this);
 }

android_webview/browser/safe_browsing/aw_safe_browsing_allowlist_manager.cc

@@ -15,7 +15,7 @@
 #include "base/strings/string_split.h"
 #include "base/strings/string_util.h"
 #include "base/task/sequenced_task_runner.h"
-#include "base/threading/thread_task_runner_handle.h"
+#include "base/task/single_thread_task_runner.h"
 #include "net/base/url_util.h"
 #include "url/url_util.h"
 
@@ -183,7 +183,7 @@ AwSafeBrowsingAllowlistManager::AwSafeBrowsingAllowlistManager(
     const scoped_refptr<base::SequencedTaskRunner>& io_task_runner)
     : background_task_runner_(background_task_runner),
       io_task_runner_(io_task_runner),
-      ui_task_runner_(base::ThreadTaskRunnerHandle::Get()),
+      ui_task_runner_(base::SingleThreadTaskRunner::GetCurrentDefault()),
       allowlist_(std::make_unique<TrieNode>()) {}
 
 AwSafeBrowsingAllowlistManager::~AwSafeBrowsingAllowlistManager() {}

android_webview/browser/safe_browsing/aw_safe_browsing_allowlist_manager_unittest.cc

@@ -10,8 +10,8 @@
 #include "base/bind.h"
 #include "base/callback.h"
 #include "base/run_loop.h"
+#include "base/task/single_thread_task_runner.h"
 #include "base/test/task_environment.h"
-#include "base/threading/thread_task_runner_handle.h"
 #include "base/values.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "url/gurl.h"
@@ -24,8 +24,8 @@ class AwSafeBrowsingAllowlistManagerTest : public testing::Test {
 
   void SetUp() override {
     wm_ = std::make_unique<AwSafeBrowsingAllowlistManager>(
-        base::ThreadTaskRunnerHandle::Get(),
-        base::ThreadTaskRunnerHandle::Get());
+        base::SingleThreadTaskRunner::GetCurrentDefault(),
+        base::SingleThreadTaskRunner::GetCurrentDefault());
   }
 
   void TearDown() override { wm_.reset(); }

android_webview/js_sandbox/service/js_sandbox_isolate.cc

@@ -20,10 +20,10 @@
 #include "base/strings/string_piece.h"
 #include "base/system/sys_info.h"
 #include "base/task/cancelable_task_tracker.h"
+#include "base/task/single_thread_task_runner.h"
 #include "base/task/thread_pool.h"
 #include "base/task/thread_pool/thread_pool_instance.h"
 #include "base/threading/thread_restrictions.h"
-#include "base/threading/thread_task_runner_handle.h"
 #include "gin/arguments.h"
 #include "gin/array_buffer.h"
 #include "gin/function_template.h"
@@ -330,7 +330,7 @@ void JsSandboxIsolate::InitializeIsolateOnThread() {
         0, AdjustToValidHeapSize(isolate_max_heap_size_bytes_));
   }
   isolate_holder_ = std::make_unique<gin::IsolateHolder>(
-      base::ThreadTaskRunnerHandle::Get(),
+      base::SingleThreadTaskRunner::GetCurrentDefault(),
       gin::IsolateHolder::AccessMode::kSingleThread,
       gin::IsolateHolder::IsolateType::kUtility, std::move(params));
   v8::Isolate* isolate = isolate_holder_->isolate();

android_webview/nonembedded/component_updater/aw_component_update_service.cc

@@ -17,7 +17,7 @@
 #include "base/check.h"
 #include "base/command_line.h"
 #include "base/no_destructor.h"
-#include "base/threading/thread_task_runner_handle.h"
+#include "base/task/single_thread_task_runner.h"
 #include "base/time/time.h"
 #include "components/component_updater/component_installer.h"
 #include "components/component_updater/component_updater_service.h"
@@ -115,7 +115,7 @@ void AwComponentUpdateService::CheckForUpdates(UpdateCallback on_finished,
   }
 
   if (unsecure_ids.empty() && secure_ids.empty()) {
-    base::ThreadTaskRunnerHandle::Get()->PostTask(
+    base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
         FROM_HERE, base::BindOnce(std::move(on_finished), 0));
     return;
   }
@@ -164,7 +164,7 @@ void AwComponentUpdateService::OnUpdateComplete(
   // CrxUpdateService once we support logging metrics from nonembedded WebView.
 
   if (!callback.is_null()) {
-    base::ThreadTaskRunnerHandle::Get()->PostTask(
+    base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
         FROM_HERE, base::BindOnce(std::move(callback), error));
   }
 }

android_webview/renderer/browser_exposed_renderer_interfaces.cc

@@ -5,7 +5,7 @@
 #include "android_webview/renderer/browser_exposed_renderer_interfaces.h"
 
 #include "android_webview/renderer/aw_content_renderer_client.h"
-#include "base/threading/thread_task_runner_handle.h"
+#include "base/task/single_thread_task_runner.h"
 #include "components/visitedlink/renderer/visitedlink_reader.h"
 #include "mojo/public/cpp/bindings/binder_map.h"
 
@@ -15,7 +15,7 @@ void ExposeRendererInterfacesToBrowser(AwContentRendererClient* client,
                                        mojo::BinderMap* binders) {
   binders->Add<visitedlink::mojom::VisitedLinkNotificationSink>(
       client->visited_link_reader()->GetBindCallback(),
-      base::ThreadTaskRunnerHandle::Get());
+      base::SingleThreadTaskRunner::GetCurrentDefault());
 }
 
 }  // namespace android_webview

apps/test/app_window_waiter.cc

@@ -4,7 +4,7 @@
 
 #include "apps/test/app_window_waiter.h"
 
-#include "base/threading/thread_task_runner_handle.h"
+#include "base/task/single_thread_task_runner.h"
 #include "extensions/browser/app_window/app_window.h"
 #include "extensions/browser/app_window/native_app_window.h"
 
@@ -52,7 +52,7 @@ extensions::AppWindow* AppWindowWaiter::WaitForShownWithTimeout(
 
   wait_type_ = WAIT_FOR_SHOWN;
   run_loop_ = std::make_unique<base::RunLoop>();
-  base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostDelayedTask(
       FROM_HERE, run_loop_->QuitClosure(), timeout);
   run_loop_->Run();
 

ash/accelerators/key_hold_detector.cc

@@ -9,7 +9,7 @@
 
 #include "ash/shell.h"
 #include "base/bind.h"
-#include "base/threading/thread_task_runner_handle.h"
+#include "base/task/single_thread_task_runner.h"
 #include "ui/aura/window_tracker.h"
 #include "ui/aura/window_tree_host.h"
 #include "ui/events/event_dispatcher.h"
@@ -36,7 +36,7 @@ void PostPressedEvent(ui::KeyEvent* event) {
   std::unique_ptr<aura::WindowTracker> tracker(new aura::WindowTracker);
   tracker->Add(static_cast<aura::Window*>(event->target()));
 
-  base::ThreadTaskRunnerHandle::Get()->PostTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
       FROM_HERE,
       base::BindOnce(&DispatchPressedEvent, pressed_event, std::move(tracker)));
 }

ash/app_list/app_list_controller_impl_unittest.cc

@@ -409,7 +409,7 @@ TEST_F(AppListControllerImplTest,
   const base::TimeDelta delta = base::Milliseconds(200);
   do {
     base::RunLoop run_loop;
-    base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
+    base::SingleThreadTaskRunner::GetCurrentDefault()->PostDelayedTask(
         FROM_HERE, run_loop.QuitClosure(), delta);
     run_loop.Run();
   } while (IsAppListBoundsAnimationRunning());

ash/app_list/views/continue_task_container_view.cc

@@ -482,7 +482,7 @@ void ContinueTaskContainerView::ScheduleUpdate() {
   // When search results are added one by one, each addition generates an update
   // request. Consolidates those update requests into one Update call.
   if (!update_factory_.HasWeakPtrs()) {
-    base::ThreadTaskRunnerHandle::Get()->PostTask(
+    base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
         FROM_HERE, base::BindOnce(&ContinueTaskContainerView::Update,
                                   update_factory_.GetWeakPtr()));
   }

ash/app_list/views/search_result_container_view.cc

@@ -7,7 +7,6 @@
 #include "base/bind.h"
 #include "base/location.h"
 #include "base/task/single_thread_task_runner.h"
-#include "base/threading/thread_task_runner_handle.h"
 
 namespace ash {
 
@@ -149,7 +148,7 @@ void SearchResultContainerView::ScheduleUpdate() {
   if (!update_factory_.HasWeakPtrs()) {
     if (delegate_)
       delegate_->OnSearchResultContainerResultsChanging();
-    base::ThreadTaskRunnerHandle::Get()->PostTask(
+    base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
         FROM_HERE, base::BindOnce(&SearchResultContainerView::Update,
                                   update_factory_.GetWeakPtr()));
   }

ash/app_list/views/top_icon_animation_view.cc

@@ -12,7 +12,7 @@
 #include "ash/public/cpp/app_list/app_list_color_provider.h"
 #include "ash/public/cpp/app_list/app_list_config.h"
 #include "ash/style/ash_color_id.h"
-#include "base/threading/thread_task_runner_handle.h"
+#include "base/task/single_thread_task_runner.h"
 #include "ui/compositor/layer.h"
 #include "ui/compositor/scoped_layer_animation_settings.h"
 #include "ui/gfx/image/image_skia_operations.h"
@@ -143,7 +143,7 @@ void TopIconAnimationView::OnImplicitAnimationsCompleted() {
   for (auto& observer : observers_)
     observer.OnTopIconAnimationsComplete(this);
   DCHECK(parent());
-  base::ThreadTaskRunnerHandle::Get()->DeleteSoon(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->DeleteSoon(
       FROM_HERE, parent()->RemoveChildViewT(this));
 }
 

ash/capture_mode/capture_label_view.cc

@@ -286,7 +286,7 @@ void CaptureLabelView::StartCountDown(
         .SetOpacity(animation_layer, 0.f);
   }
 
-  base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostDelayedTask(
       FROM_HERE,
       base::BindOnce(&CaptureLabelView::FadeInAndOutCounter,
                      weak_factory_.GetWeakPtr(), kCountDownStartSeconds),

ash/capture_mode/capture_mode_test_util.cc

@@ -110,7 +110,7 @@ void SendKey(ui::KeyboardCode key_code,
 
 void WaitForSeconds(int seconds) {
   base::RunLoop loop;
-  base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostDelayedTask(
       FROM_HERE, loop.QuitClosure(), base::Seconds(seconds));
   loop.Run();
 }

ash/capture_mode/capture_mode_util.cc

@@ -226,7 +226,7 @@ void TriggerAccessibilityAlert(int message_id) {
 }
 
 void TriggerAccessibilityAlertSoon(const std::string& message) {
-  base::ThreadTaskRunnerHandle::Get()->PostTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
       FROM_HERE,
       base::BindOnce(
           &AccessibilityControllerImpl::TriggerAccessibilityAlertWithMessage,

ash/capture_mode/fake_video_source_provider.cc

@@ -6,7 +6,7 @@
 
 #include "base/check.h"
 #include "base/system/system_monitor.h"
-#include "base/threading/thread_task_runner_handle.h"
+#include "base/task/single_thread_task_runner.h"
 #include "media/base/video_types.h"
 #include "media/capture/video/video_capture_device_descriptor.h"
 #include "media/capture/video_capture_types.h"
@@ -111,7 +111,7 @@ void FakeVideoSourceProvider::GetSourceInfos(GetSourceInfosCallback callback) {
 
   // Simulate the asynchronously behavior of the actual VideoSourceProvider
   // which does a lot of asynchronous and mojo calls.
-  base::ThreadTaskRunnerHandle::Get()->PostTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
       FROM_HERE, base::BindOnce(std::move(callback), devices));
 
   if (on_replied_with_source_infos_)

ash/child_accounts/parent_access_controller_impl.cc

@@ -264,7 +264,7 @@ void ParentAccessControllerImpl::OnHelp() {
   RecordParentAccessAction(ParentAccessControllerImpl::UMAAction::kGetHelp);
   // TODO(https://crbug.com/999387): Remove this when handling touch
   // cancellation is fixed for system modal windows.
-  base::ThreadTaskRunnerHandle::Get()->PostTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
       FROM_HERE, base::BindOnce([]() {
         Shell::Get()->login_screen_controller()->ShowParentAccessHelpApp();
       }));

ash/clipboard/clipboard_history_controller_impl.cc

@@ -36,8 +36,8 @@
 #include "base/synchronization/lock.h"
 #include "base/task/bind_post_task.h"
 #include "base/task/sequenced_task_runner.h"
+#include "base/task/single_thread_task_runner.h"
 #include "base/task/thread_pool.h"
-#include "base/threading/thread_task_runner_handle.h"
 #include "base/unguessable_token.h"
 #include "base/values.h"
 #include "third_party/abseil-cpp/absl/types/optional.h"
@@ -904,7 +904,7 @@ void ClipboardHistoryControllerImpl::PasteClipboardHistoryItem(
   // Replace the clipboard data. Some apps take a long time to receive the paste
   // event, and some apps will read from the clipboard multiple times per paste.
   // Wait a bit before writing `data_to_restore` back to the clipboard.
-  base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostDelayedTask(
       FROM_HERE,
       base::BindOnce(
           [](const base::WeakPtr<ClipboardHistoryControllerImpl>& weak_ptr,

ash/components/arc/enterprise/arc_data_snapshotd_bridge.cc

@@ -8,7 +8,7 @@
 
 #include "base/bind.h"
 #include "base/logging.h"
-#include "base/threading/thread_task_runner_handle.h"
+#include "base/task/single_thread_task_runner.h"
 #include "chromeos/ash/components/dbus/arc/arc_data_snapshotd_client.h"
 
 namespace arc {
@@ -62,7 +62,7 @@ void ArcDataSnapshotdBridge::WaitForDBusService() {
 }
 
 void ArcDataSnapshotdBridge::ScheduleWaitingForDBusService() {
-  base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostDelayedTask(
       FROM_HERE,
       base::BindOnce(&ArcDataSnapshotdBridge::WaitForDBusService,
                      dbus_waiting_weak_ptr_factory_.GetWeakPtr()),

ash/components/arc/ime/key_event_result_receiver.cc

@@ -8,7 +8,7 @@
 #include "base/bind.h"
 #include "base/callback.h"
 #include "base/logging.h"
-#include "base/threading/thread_task_runner_handle.h"
+#include "base/task/single_thread_task_runner.h"
 #include "base/time/time.h"
 #include "third_party/abseil-cpp/absl/types/optional.h"
 #include "ui/events/base_event_utils.h"
@@ -80,7 +80,7 @@ void KeyEventResultReceiver::SetCallback(KeyEventDoneCallback callback,
   callback_ = std::move(callback);
   expected_key_event_ = *event;
   // Start expiring timer for the callback.
-  base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostDelayedTask(
       FROM_HERE,
       base::BindOnce(&KeyEventResultReceiver::ExpireCallback,
                      weak_ptr_factory_.GetWeakPtr()),

ash/components/arc/session/arc_container_client_adapter.cc

@@ -12,7 +12,7 @@
 #include "base/callback_helpers.h"
 #include "base/logging.h"
 #include "base/notreached.h"
-#include "base/threading/thread_task_runner_handle.h"
+#include "base/task/single_thread_task_runner.h"
 #include "chromeos/ash/components/cryptohome/cryptohome_parameters.h"
 #include "chromeos/ash/components/dbus/arc/arc.pb.h"
 #include "chromeos/ash/components/dbus/session_manager/session_manager_client.h"
@@ -142,7 +142,7 @@ class ArcContainerClientAdapter : public ArcClientAdapter,
   // The interface is only for ARCVM.
   void TrimVmMemory(TrimVmMemoryCallback callback, int) override {
     NOTREACHED();
-    base::ThreadTaskRunnerHandle::Get()->PostTask(
+    base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
         FROM_HERE,
         base::BindOnce(std::move(callback), /*success=*/true,
                        /*failure_reason=*/"ARC container is not supported."));

ash/components/arc/session/arc_data_remover_unittest.cc

@@ -12,8 +12,8 @@
 #include "ash/components/arc/arc_prefs.h"
 #include "base/bind.h"
 #include "base/run_loop.h"
+#include "base/task/single_thread_task_runner.h"
 #include "base/test/task_environment.h"
-#include "base/threading/thread_task_runner_handle.h"
 #include "chromeos/ash/components/cryptohome/cryptohome_parameters.h"
 #include "chromeos/ash/components/dbus/upstart/fake_upstart_client.h"
 #include "components/account_id/account_id.h"
@@ -35,7 +35,7 @@ class TestUpstartClient : public ash::FakeUpstartClient {
   void StartJob(const std::string& job,
                 const std::vector<std::string>& upstart_env,
                 chromeos::VoidDBusMethodCallback callback) override {
-    base::ThreadTaskRunnerHandle::Get()->PostTask(
+    base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
         FROM_HERE, base::BindOnce(std::move(callback), arc_available_));
   }
 

ash/components/arc/session/arc_session_impl_unittest.cc

@@ -22,9 +22,9 @@
 #include "base/files/file_path.h"
 #include "base/location.h"
 #include "base/run_loop.h"
+#include "base/task/single_thread_task_runner.h"
 #include "base/test/scoped_feature_list.h"
 #include "base/test/task_environment.h"
-#include "base/threading/thread_task_runner_handle.h"
 #include "chromeos/system/scheduler_configuration_manager_base.h"
 #include "components/version_info/channel.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ -65,7 +65,7 @@ class FakeArcClientAdapter : public ArcClientAdapter {
   void StartMiniArc(StartParams params,
                     chromeos::VoidDBusMethodCallback callback) override {
     last_start_params_ = std::move(params);
-    base::ThreadTaskRunnerHandle::Get()->PostTask(
+    base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
         FROM_HERE, base::BindOnce(&FakeArcClientAdapter::OnMiniArcStarted,
                                   base::Unretained(this), std::move(callback),
                                   arc_available_));
@@ -74,14 +74,14 @@ class FakeArcClientAdapter : public ArcClientAdapter {
   void UpgradeArc(UpgradeParams params,
                   chromeos::VoidDBusMethodCallback callback) override {
     last_upgrade_params_ = std::move(params);
-    base::ThreadTaskRunnerHandle::Get()->PostTask(
+    base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
         FROM_HERE, base::BindOnce(&FakeArcClientAdapter::OnArcUpgraded,
                                   base::Unretained(this), std::move(callback),
                                   !force_upgrade_failure_));
   }
 
   void StopArcInstance(bool on_shutdown, bool should_backup_log) override {
-    base::ThreadTaskRunnerHandle::Get()->PostTask(
+    base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
         FROM_HERE,
         base::BindOnce(&FakeArcClientAdapter::NotifyArcInstanceStopped,
                        base::Unretained(this), false /* is_system_shutdown */));
@@ -93,7 +93,7 @@ class FakeArcClientAdapter : public ArcClientAdapter {
 
   void SetDemoModeDelegate(DemoModeDelegate* delegate) override {}
   void TrimVmMemory(TrimVmMemoryCallback callback, int page_limit) override {
-    base::ThreadTaskRunnerHandle::Get()->PostTask(
+    base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
         FROM_HERE, base::BindOnce(std::move(callback), true, std::string()));
   }
 
@@ -157,7 +157,7 @@ class FakeDelegate : public ArcSessionImpl::Delegate {
   // ArcSessionImpl::Delegate overrides:
   void CreateSocket(CreateSocketCallback callback) override {
     // Open /dev/null as a dummy FD.
-    base::ThreadTaskRunnerHandle::Get()->PostTask(
+    base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
         FROM_HERE, base::BindOnce(std::move(callback),
                                   base::ScopedFD(open("/dev/null",
                                                       O_RDONLY | O_CLOEXEC))));
@@ -192,7 +192,7 @@ class FakeDelegate : public ArcSessionImpl::Delegate {
 
  private:
   void PostCallback(ConnectMojoCallback callback) {
-    base::ThreadTaskRunnerHandle::Get()->PostTask(
+    base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
         FROM_HERE,
         base::BindOnce(
             std::move(callback),

ash/components/arc/session/arc_vm_client_adapter.cc

@@ -48,11 +48,11 @@
 #include "base/strings/string_util.h"
 #include "base/strings/stringprintf.h"
 #include "base/system/sys_info.h"
+#include "base/task/single_thread_task_runner.h"
 #include "base/task/task_traits.h"
 #include "base/task/thread_pool.h"
 #include "base/threading/platform_thread.h"
 #include "base/threading/scoped_blocking_call.h"
-#include "base/threading/thread_task_runner_handle.h"
 #include "base/time/time.h"
 #include "base/timer/elapsed_timer.h"
 #include "chromeos/ash/components/cryptohome/cryptohome_parameters.h"
@@ -887,7 +887,7 @@ class ArcVmClientAdapter : public ArcClientAdapter,
   void TrimVmMemory(TrimVmMemoryCallback callback, int page_limit) override {
     VLOG(2) << "Start trimming VM memory";
     if (user_id_hash_.empty()) {
-      base::ThreadTaskRunnerHandle::Get()->PostTask(
+      base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
           FROM_HERE,
           base::BindOnce(std::move(callback), /*success=*/false,
                          /*failure_reason=*/"user_id_hash_ is not set"));

ash/components/arc/test/fake_file_system_instance.cc

@@ -20,7 +20,7 @@
 #include "base/location.h"
 #include "base/logging.h"
 #include "base/ranges/algorithm.h"
-#include "base/threading/thread_task_runner_handle.h"
+#include "base/task/single_thread_task_runner.h"
 #include "mojo/public/cpp/system/platform_handle.h"
 #include "third_party/abseil-cpp/absl/types/optional.h"
 
@@ -352,14 +352,14 @@ void FakeFileSystemInstance::AddWatcher(const std::string& authority,
   DocumentKey key(authority, document_id);
   auto iter = documents_.find(key);
   if (iter == documents_.end()) {
-    base::ThreadTaskRunnerHandle::Get()->PostTask(
+    base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
         FROM_HERE, base::BindOnce(std::move(callback), -1));
     return;
   }
   int64_t watcher_id = next_watcher_id_++;
   document_to_watchers_[key].insert(watcher_id);
   watcher_to_document_.insert(std::make_pair(watcher_id, key));
-  base::ThreadTaskRunnerHandle::Get()->PostTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
       FROM_HERE, base::BindOnce(std::move(callback), watcher_id));
 }
 
@@ -368,12 +368,12 @@ void FakeFileSystemInstance::GetFileSize(const std::string& url,
   DCHECK_CALLED_ON_VALID_THREAD(thread_checker_);
   auto iter = files_.find(url);
   if (iter == files_.end()) {
-    base::ThreadTaskRunnerHandle::Get()->PostTask(
+    base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
         FROM_HERE, base::BindOnce(std::move(callback), -1));
     return;
   }
   const File& file = iter->second;
-  base::ThreadTaskRunnerHandle::Get()->PostTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
       FROM_HERE, base::BindOnce(std::move(callback), file.size()));
 }
 
@@ -382,12 +382,12 @@ void FakeFileSystemInstance::GetMimeType(const std::string& url,
   DCHECK_CALLED_ON_VALID_THREAD(thread_checker_);
   auto iter = files_.find(url);
   if (iter == files_.end()) {
-    base::ThreadTaskRunnerHandle::Get()->PostTask(
+    base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
         FROM_HERE, base::BindOnce(std::move(callback), absl::nullopt));
     return;
   }
   const File& file = iter->second;
-  base::ThreadTaskRunnerHandle::Get()->PostTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
       FROM_HERE, base::BindOnce(std::move(callback), file.mime_type));
 }
 
@@ -407,7 +407,7 @@ void FakeFileSystemInstance::OpenFileSessionToWrite(
   DCHECK_CALLED_ON_VALID_THREAD(thread_checker_);
   auto iter = files_.find(url.spec());
   if (iter == files_.end()) {
-    base::ThreadTaskRunnerHandle::Get()->PostTask(
+    base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
         FROM_HERE,
         base::BindOnce(std::move(callback), mojom::FileSessionPtr()));
     return;
@@ -427,7 +427,7 @@ void FakeFileSystemInstance::OpenFileSessionToWrite(
   mojom::FileSessionPtr file_session = mojom::FileSession::New();
   file_session->url_id = std::move(url_id);
   file_session->fd = std::move(wrapped_handle);
-  base::ThreadTaskRunnerHandle::Get()->PostTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
       FROM_HERE, base::BindOnce(std::move(callback), std::move(file_session)));
 }
 
@@ -437,7 +437,7 @@ void FakeFileSystemInstance::OpenFileSessionToRead(
   DCHECK_CALLED_ON_VALID_THREAD(thread_checker_);
   auto iter = files_.find(url.spec());
   if (iter == files_.end()) {
-    base::ThreadTaskRunnerHandle::Get()->PostTask(
+    base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
         FROM_HERE,
         base::BindOnce(std::move(callback), mojom::FileSessionPtr()));
     return;
@@ -457,7 +457,7 @@ void FakeFileSystemInstance::OpenFileSessionToRead(
   mojom::FileSessionPtr file_session = mojom::FileSession::New();
   file_session->url_id = std::move(url_id);
   file_session->fd = std::move(wrapped_handle);
-  base::ThreadTaskRunnerHandle::Get()->PostTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
       FROM_HERE, base::BindOnce(std::move(callback), std::move(file_session)));
 }
 
@@ -467,13 +467,13 @@ void FakeFileSystemInstance::OpenThumbnail(const std::string& url,
   DCHECK_CALLED_ON_VALID_THREAD(thread_checker_);
   auto iter = files_.find(url);
   if (iter == files_.end()) {
-    base::ThreadTaskRunnerHandle::Get()->PostTask(
+    base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
         FROM_HERE, base::BindOnce(std::move(callback), mojo::ScopedHandle()));
     return;
   }
   const File& file = iter->second;
   if (file.thumbnail_content.empty()) {
-    base::ThreadTaskRunnerHandle::Get()->PostTask(
+    base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
         FROM_HERE, base::BindOnce(std::move(callback), mojo::ScopedHandle()));
     return;
   }
@@ -483,7 +483,7 @@ void FakeFileSystemInstance::OpenThumbnail(const std::string& url,
   if (size_hint != kDefaultThumbnailSize) {
     LOG(ERROR) << "Unexpected thumbnail size hint: " << size_hint.width() << "x"
                << size_hint.height();
-    base::ThreadTaskRunnerHandle::Get()->PostTask(
+    base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
         FROM_HERE, base::BindOnce(std::move(callback), mojo::ScopedHandle()));
     return;
   }
@@ -491,7 +491,7 @@ void FakeFileSystemInstance::OpenThumbnail(const std::string& url,
   mojo::ScopedHandle wrapped_handle =
       mojo::WrapPlatformHandle(mojo::PlatformHandle(std::move(fd)));
   DCHECK(wrapped_handle.is_valid());
-  base::ThreadTaskRunnerHandle::Get()->PostTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
       FROM_HERE,
       base::BindOnce(std::move(callback), std::move(wrapped_handle)));
 }
@@ -502,11 +502,11 @@ void FakeFileSystemInstance::GetDocument(const std::string& authority,
   DCHECK_CALLED_ON_VALID_THREAD(thread_checker_);
   auto iter = documents_.find(DocumentKey(authority, document_id));
   if (iter == documents_.end()) {
-    base::ThreadTaskRunnerHandle::Get()->PostTask(
+    base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
         FROM_HERE, base::BindOnce(std::move(callback), mojom::DocumentPtr()));
     return;
   }
-  base::ThreadTaskRunnerHandle::Get()->PostTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
       FROM_HERE,
       base::BindOnce(std::move(callback), MakeDocument(iter->second)));
 }
@@ -520,7 +520,7 @@ void FakeFileSystemInstance::GetChildDocuments(
   auto child_iter =
       child_documents_.find(DocumentKey(authority, parent_document_id));
   if (child_iter == child_documents_.end()) {
-    base::ThreadTaskRunnerHandle::Get()->PostTask(
+    base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
         FROM_HERE, base::BindOnce(std::move(callback), absl::nullopt));
     return;
   }
@@ -530,7 +530,7 @@ void FakeFileSystemInstance::GetChildDocuments(
     DCHECK(doc_iter != documents_.end());
     children.emplace_back(MakeDocument(doc_iter->second));
   }
-  base::ThreadTaskRunnerHandle::Get()->PostTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
       FROM_HERE, base::BindOnce(std::move(callback),
                                 absl::make_optional(std::move(children))));
 }
@@ -542,14 +542,14 @@ void FakeFileSystemInstance::GetRecentDocuments(
   DCHECK_CALLED_ON_VALID_THREAD(thread_checker_);
   auto recent_iter = recent_documents_.find(RootKey(authority, root_id));
   if (recent_iter == recent_documents_.end()) {
-    base::ThreadTaskRunnerHandle::Get()->PostTask(
+    base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
         FROM_HERE, base::BindOnce(std::move(callback), absl::nullopt));
     return;
   }
   std::vector<mojom::DocumentPtr> recents;
   for (const Document& document : recent_iter->second)
     recents.emplace_back(MakeDocument(document));
-  base::ThreadTaskRunnerHandle::Get()->PostTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
       FROM_HERE, base::BindOnce(std::move(callback),
                                 absl::make_optional(std::move(recents))));
 }
@@ -559,7 +559,7 @@ void FakeFileSystemInstance::GetRoots(GetRootsCallback callback) {
   std::vector<mojom::RootPtr> roots;
   for (const Root& root : roots_list_)
     roots.emplace_back(MakeRoot(root));
-  base::ThreadTaskRunnerHandle::Get()->PostTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
       FROM_HERE, base::BindOnce(std::move(callback),
                                 absl::make_optional(std::move(roots))));
 }
@@ -570,7 +570,7 @@ void FakeFileSystemInstance::GetRootSize(const std::string& authority,
   DCHECK_CALLED_ON_VALID_THREAD(thread_checker_);
   auto iter = roots_.find(RootKey(authority, root_id));
   if (iter == roots_.end()) {
-    base::ThreadTaskRunnerHandle::Get()->PostTask(
+    base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
         FROM_HERE, base::BindOnce(std::move(callback), mojom::RootSizePtr()));
     return;
   }
@@ -578,7 +578,7 @@ void FakeFileSystemInstance::GetRootSize(const std::string& authority,
   mojom::RootSizePtr root_size = mojom::RootSize::New();
   root_size->available_bytes = root.available_bytes;
   root_size->capacity_bytes = root.capacity_bytes;
-  base::ThreadTaskRunnerHandle::Get()->PostTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
       FROM_HERE, base::BindOnce(std::move(callback), std::move(root_size)));
 }
 
@@ -589,7 +589,7 @@ void FakeFileSystemInstance::DeleteDocument(const std::string& authority,
   DocumentKey key(authority, document_id);
   auto iter = documents_.find(key);
   if (iter == documents_.end() || iter->second.supports_delete == false) {
-    base::ThreadTaskRunnerHandle::Get()->PostTask(
+    base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
         FROM_HERE, base::BindOnce(std::move(callback), false));
     return;
   }
@@ -599,7 +599,7 @@ void FakeFileSystemInstance::DeleteDocument(const std::string& authority,
   documents_.erase(iter);
   size_t erased = child_documents_.erase(key);
   DCHECK_NE(0u, erased);
-  base::ThreadTaskRunnerHandle::Get()->PostTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
       FROM_HERE, base::BindOnce(std::move(callback), true));
 }
 
@@ -611,12 +611,12 @@ void FakeFileSystemInstance::RenameDocument(const std::string& authority,
   DocumentKey key(authority, document_id);
   auto iter = documents_.find(key);
   if (iter == documents_.end() || iter->second.supports_rename == false) {
-    base::ThreadTaskRunnerHandle::Get()->PostTask(
+    base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
         FROM_HERE, base::BindOnce(std::move(callback), mojom::DocumentPtr()));
     return;
   }
   iter->second.display_name = display_name;
-  base::ThreadTaskRunnerHandle::Get()->PostTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
       FROM_HERE,
       base::BindOnce(std::move(callback), MakeDocument(iter->second)));
 }
@@ -632,7 +632,7 @@ void FakeFileSystemInstance::CreateDocument(
   auto iter = documents_.find(parent_key);
   DCHECK(iter != documents_.end());
   if (iter->second.dir_supports_create == false) {
-    base::ThreadTaskRunnerHandle::Get()->PostTask(
+    base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
         FROM_HERE, base::BindOnce(std::move(callback), mojom::DocumentPtr()));
     return;
   }
@@ -640,7 +640,7 @@ void FakeFileSystemInstance::CreateDocument(
   Document document(authority, document_id, parent_document_id, display_name,
                     mime_type, 0, 0);
   AddDocument(document);
-  base::ThreadTaskRunnerHandle::Get()->PostTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
       FROM_HERE, base::BindOnce(std::move(callback), MakeDocument(document)));
 }
 
@@ -657,7 +657,7 @@ void FakeFileSystemInstance::CopyDocument(
   target_document.document_id = target_document.display_name;
   target_document.parent_document_id = target_parent_document_id;
   AddDocument(target_document);
-  base::ThreadTaskRunnerHandle::Get()->PostTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
       FROM_HERE,
       base::BindOnce(std::move(callback), MakeDocument(target_document)));
 }
@@ -683,7 +683,7 @@ void FakeFileSystemInstance::MoveDocument(
   auto iter = documents_.find(source_key);
   DCHECK(iter != documents_.end());
   iter->second.parent_document_id = target_parent_document_id;
-  base::ThreadTaskRunnerHandle::Get()->PostTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
       FROM_HERE,
       base::BindOnce(std::move(callback), MakeDocument(iter->second)));
 }
@@ -703,13 +703,13 @@ void FakeFileSystemInstance::RemoveWatcher(int64_t watcher_id,
   DCHECK_CALLED_ON_VALID_THREAD(thread_checker_);
   auto iter = watcher_to_document_.find(watcher_id);
   if (iter == watcher_to_document_.end()) {
-    base::ThreadTaskRunnerHandle::Get()->PostTask(
+    base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
         FROM_HERE, base::BindOnce(std::move(callback), false));
     return;
   }
   document_to_watchers_[iter->second].erase(watcher_id);
   watcher_to_document_.erase(iter);
-  base::ThreadTaskRunnerHandle::Get()->PostTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
       FROM_HERE, base::BindOnce(std::move(callback), true));
 }
 

ash/components/arc/test/fake_process_instance.cc

@@ -8,7 +8,7 @@
 #include <utility>
 
 #include "base/check_op.h"
-#include "base/threading/thread_task_runner_handle.h"
+#include "base/task/single_thread_task_runner.h"
 
 namespace arc {
 
@@ -53,7 +53,7 @@ void FakeProcessInstance::ApplyHostMemoryPressure(
   host_memory_pressure_reclaim_target_ = reclaim_target;
 
   DCHECK(host_memory_pressure_response_);
-  base::ThreadTaskRunnerHandle::Get()->PostTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
       FROM_HERE,
       base::BindOnce(std::move(callback), host_memory_pressure_response_->first,
                      host_memory_pressure_response_->second));
@@ -63,7 +63,7 @@ void FakeProcessInstance::ApplyHostMemoryPressure(
 void FakeProcessInstance::RequestLowMemoryKillCounts(
     RequestLowMemoryKillCountsCallback callback) {
   DCHECK(low_memory_kill_counts_response_);
-  base::ThreadTaskRunnerHandle::Get()->PostTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
       FROM_HERE, base::BindOnce(std::move(callback),
                                 std::move(*low_memory_kill_counts_response_)));
 }

ash/components/arc/video_accelerator/gpu_arc_video_decode_accelerator.cc

@@ -550,7 +550,7 @@ void GpuArcVideoDecodeAccelerator::ContinueDecode(
       // Note: we PostTask() in order to keep the right order of input buffers
       // and to avoid having to reason about the re-entrancy of Decode() and/or
       // ContinueDecode().
-      base::ThreadTaskRunnerHandle::Get()->PostTask(
+      base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
           FROM_HERE,
           base::BindOnce(&GpuArcVideoDecodeAccelerator::
                              ResumeDecodingAfterFirstSecureBuffer,

ash/components/arc/video_accelerator/gpu_arc_video_decoder.cc

@@ -82,7 +82,7 @@ void GpuArcVideoDecoder::Initialize(
   DCHECK(!error_state_);
   DCHECK(!client_ && !init_callback_ && !video_frame_pool_);
 
-  client_task_runner_ = base::ThreadTaskRunnerHandle::Get();
+  client_task_runner_ = base::SingleThreadTaskRunner::GetCurrentDefault();
   client_.Bind(std::move(client));
   init_callback_ = std::move(callback);
   video_frame_pool_ = std::make_unique<GpuArcVideoFramePool>(

ash/components/arc/video_accelerator/gpu_arc_video_frame_pool.cc

@@ -71,7 +71,7 @@ GpuArcVideoFramePool::GpuArcVideoFramePool(
 
   weak_this_ = weak_this_factory_.GetWeakPtr();
 
-  client_task_runner_ = base::ThreadTaskRunnerHandle::Get();
+  client_task_runner_ = base::SingleThreadTaskRunner::GetCurrentDefault();
   vda_video_frame_pool_ = std::make_unique<media::VdaVideoFramePool>(
       weak_this_, client_task_runner_);
 }

ash/components/arc/volume_mounter/arc_volume_mounter_bridge.cc

@@ -23,7 +23,7 @@
 #include "base/strings/string_util.h"
 #include "base/strings/stringprintf.h"
 #include "base/task/bind_post_task.h"
-#include "base/threading/thread_task_runner_handle.h"
+#include "base/task/single_thread_task_runner.h"
 #include "chromeos/ash/components/cryptohome/cryptohome_parameters.h"
 #include "chromeos/ash/components/dbus/upstart/upstart_client.h"
 #include "chromeos/ash/components/disks/disk.h"
@@ -330,7 +330,7 @@ void ArcVolumeMounterBridge::RequestAllMountPoints() {
   // Deferring the SendAllMountEvents as a task to current thread to not
   // block the mojo request since SendAllMountEvents might take non trivial
   // amount of time.
-  base::ThreadTaskRunnerHandle::Get()->PostTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
       FROM_HERE, base::BindOnce(&ArcVolumeMounterBridge::SendAllMountEvents,
                                 weak_ptr_factory_.GetWeakPtr()));
 }
@@ -384,7 +384,7 @@ void ArcVolumeMounterBridge::SetUpExternalStorageMountPoints(
   ash::UpstartClient::Get()->StartJobWithErrorDetails(
       kArcVmMediaSharingServicesJobName, std::move(environment),
       base::BindPostTask(
-          base::ThreadTaskRunnerHandle::Get(),
+          base::SingleThreadTaskRunner::GetCurrentDefault(),
           base::BindOnce(
               &ArcVolumeMounterBridge::OnSetUpExternalStorageMountPoints,
               weak_ptr_factory_.GetWeakPtr(), std::move(callback))));

ash/display/display_animator.cc

@@ -10,7 +10,7 @@
 #include "ash/shell.h"
 #include "base/bind.h"
 #include "base/memory/ptr_util.h"
-#include "base/threading/thread_task_runner_handle.h"
+#include "base/task/single_thread_task_runner.h"
 #include "base/time/time.h"
 #include "ui/aura/window.h"
 #include "ui/aura/window_event_dispatcher.h"
@@ -48,10 +48,11 @@ class CallbackRunningObserver {
   void OnSingleTaskCompleted() {
     completed_counter_++;
     if (completed_counter_ >= observer_list_.size()) {
-      base::ThreadTaskRunnerHandle::Get()->DeleteSoon(FROM_HERE, this);
+      base::SingleThreadTaskRunner::GetCurrentDefault()->DeleteSoon(FROM_HERE,
+                                                                    this);
       if (!animation_aborted_)
-        base::ThreadTaskRunnerHandle::Get()->PostTask(FROM_HERE,
-                                                      std::move(callback_));
+        base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
+            FROM_HERE, std::move(callback_));
     }
   }
 

ash/display/display_configuration_observer.cc

@@ -11,7 +11,7 @@
 #include "ash/wm/tablet_mode/tablet_mode_controller.h"
 #include "base/bind.h"
 #include "base/command_line.h"
-#include "base/threading/thread_task_runner_handle.h"
+#include "base/task/single_thread_task_runner.h"
 #include "ui/display/manager/display_layout_store.h"
 #include "ui/display/manager/display_manager.h"
 
@@ -42,14 +42,14 @@ void DisplayConfigurationObserver::OnTabletModeStarted() {
   // Setting mirror mode may destroy the secondary SystemTray, so use
   // PostTask to set mirror mode in the next frame in case other
   // TabletModeObserver entries are owned by the SystemTray.
-  base::ThreadTaskRunnerHandle::Get()->PostTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
       FROM_HERE, base::BindOnce(&DisplayConfigurationObserver::StartMirrorMode,
                                 weak_ptr_factory_.GetWeakPtr()));
 }
 
 void DisplayConfigurationObserver::OnTabletModeEnded() {
   // See comment for OnTabletModeStarted.
-  base::ThreadTaskRunnerHandle::Get()->PostTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
       FROM_HERE, base::BindOnce(&DisplayConfigurationObserver::EndMirrorMode,
                                 weak_ptr_factory_.GetWeakPtr()));
 }

ash/display/mirror_window_controller.cc

@@ -18,7 +18,7 @@
 #include "ash/shell.h"
 #include "base/containers/contains.h"
 #include "base/strings/stringprintf.h"
-#include "base/threading/thread_task_runner_handle.h"
+#include "base/task/single_thread_task_runner.h"
 #include "components/viz/common/surfaces/surface_id.h"
 #include "ui/aura/client/capture_client.h"
 #include "ui/aura/window.h"
@@ -425,7 +425,8 @@ void MirrorWindowController::CloseAndDeleteHost(MirroringHostInfo* host_info,
   // was deleted as a result of input event (e.g. shortcut), so don't delete
   // now.
   if (delay_host_deletion)
-    base::ThreadTaskRunnerHandle::Get()->DeleteSoon(FROM_HERE, host_info);
+    base::SingleThreadTaskRunner::GetCurrentDefault()->DeleteSoon(FROM_HERE,
+                                                                  host_info);
   else
     delete host_info;
 }

ash/display/touch_calibrator_controller.cc

@@ -13,7 +13,7 @@
 #include "ash/touch/ash_touch_transform_controller.h"
 #include "base/bind.h"
 #include "base/ranges/algorithm.h"
-#include "base/threading/thread_task_runner_handle.h"
+#include "base/task/single_thread_task_runner.h"
 #include "ui/aura/window_tree_host.h"
 #include "ui/display/manager/touch_device_manager.h"
 #include "ui/display/screen.h"
@@ -158,7 +158,7 @@ void TouchCalibratorController::StopCalibrationAndResetParams() {
   state_ = CalibrationState::kInactive;
 
   if (opt_callback_) {
-    base::ThreadTaskRunnerHandle::Get()->PostTask(
+    base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
         FROM_HERE,
         base::BindOnce(std::move(opt_callback_), false /* failure */));
     opt_callback_.Reset();
@@ -187,7 +187,7 @@ void TouchCalibratorController::CompleteCalibration(
   }
 
   if (opt_callback_) {
-    base::ThreadTaskRunnerHandle::Get()->PostTask(
+    base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
         FROM_HERE,
         base::BindOnce(std::move(opt_callback_), true /* success */));
     opt_callback_.Reset();

ash/display/window_tree_host_manager.cc

@@ -32,7 +32,7 @@
 #include "base/notreached.h"
 #include "base/strings/stringprintf.h"
 #include "base/strings/utf_string_conversions.h"
-#include "base/threading/thread_task_runner_handle.h"
+#include "base/task/single_thread_task_runner.h"
 #include "ui/aura/client/capture_client.h"
 #include "ui/aura/client/focus_client.h"
 #include "ui/aura/client/screen_position_client.h"
@@ -610,7 +610,8 @@ void WindowTreeHostManager::DeleteHost(AshWindowTreeHost* host_to_delete) {
     Shell::SetRootWindowForNewWindows(primary_root_after_host_deletion);
   }
   // NOTE: ShelfWidget is gone, but Shelf still exists until this task runs.
-  base::ThreadTaskRunnerHandle::Get()->DeleteSoon(FROM_HERE, controller);
+  base::SingleThreadTaskRunner::GetCurrentDefault()->DeleteSoon(FROM_HERE,
+                                                                controller);
 }
 
 void WindowTreeHostManager::OnDisplayRemoved(const display::Display& display) {

ash/drag_drop/drag_drop_controller.cc

@@ -13,8 +13,8 @@
 #include "ash/wm/window_util.h"
 #include "base/bind.h"
 #include "base/run_loop.h"
+#include "base/task/single_thread_task_runner.h"
 #include "base/threading/hang_watcher.h"
-#include "base/threading/thread_task_runner_handle.h"
 #include "ui/aura/client/capture_client.h"
 #include "ui/aura/client/drag_drop_client_observer.h"
 #include "ui/aura/client/drag_drop_delegate.h"
@@ -766,7 +766,7 @@ void DragDropController::ScheduleForwardPendingLongTap() {
   }
 
   // See comment about this in OnGestureEvent().
-  base::ThreadTaskRunnerHandle::Get()->PostTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
       FROM_HERE, base::BindOnce(&DragDropController::ForwardPendingLongTap,
                                 weak_factory_.GetWeakPtr()));
 }

ash/drag_drop/drag_drop_controller_unittest.cc

@@ -22,10 +22,10 @@
 #include "base/notreached.h"
 #include "base/run_loop.h"
 #include "base/strings/utf_string_conversions.h"
+#include "base/task/single_thread_task_runner.h"
 #include "base/test/bind.h"
 #include "base/test/gmock_callback_support.h"
 #include "base/test/scoped_feature_list.h"
-#include "base/threading/thread_task_runner_handle.h"
 #include "testing/gmock/include/gmock/gmock.h"
 #include "third_party/abseil-cpp/absl/types/optional.h"
 #include "ui/aura/client/capture_client.h"
@@ -1320,15 +1320,15 @@ TEST_F(DragDropControllerTest, EventTarget) {
   ui::test::EventGenerator generator(window->GetRootWindow(), window.get());
   generator.PressLeftButton();
   // For drag enter
-  base::ThreadTaskRunnerHandle::Get()->PostTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
       FROM_HERE, base::BindOnce(&ui::test::EventGenerator::MoveMouseBy,
                                 base::Unretained(&generator), 0, 1));
   // For drag update
-  base::ThreadTaskRunnerHandle::Get()->PostTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
       FROM_HERE, base::BindOnce(&ui::test::EventGenerator::MoveMouseBy,
                                 base::Unretained(&generator), 0, 1));
   // For perform drop
-  base::ThreadTaskRunnerHandle::Get()->PostTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
       FROM_HERE, base::BindOnce(&ui::test::EventGenerator::ReleaseLeftButton,
                                 base::Unretained(&generator)));
 
@@ -1363,11 +1363,11 @@ TEST_F(DragDropControllerTest, DragTabChangesDragOperationToMove) {
   ui::test::EventGenerator generator(window->GetRootWindow(), window);
   generator.PressLeftButton();
   // For drag enter.
-  base::ThreadTaskRunnerHandle::Get()->PostTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
       FROM_HERE, base::BindOnce(&ui::test::EventGenerator::MoveMouseBy,
                                 base::Unretained(&generator), 0, 1));
   // For perform drop.
-  base::ThreadTaskRunnerHandle::Get()->PostTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
       FROM_HERE, base::BindOnce(&ui::test::EventGenerator::ReleaseLeftButton,
                                 base::Unretained(&generator)));
 

ash/fast_ink/cursor/cursor_view.cc

@@ -6,8 +6,8 @@
 
 #include "base/bind.h"
 #include "base/memory/ptr_util.h"
+#include "base/task/single_thread_task_runner.h"
 #include "base/task/thread_pool.h"
-#include "base/threading/thread_task_runner_handle.h"
 #include "base/trace_event/trace_event.h"
 #include "cc/paint/paint_canvas.h"
 #include "ui/aura/window.h"
@@ -60,7 +60,7 @@ gfx::Vector2dF InterpolateBetween(const gfx::Vector2dF& start,
 CursorView::CursorView(const gfx::Point& initial_location,
                        bool is_motion_blur_enabled)
     : is_motion_blur_enabled_(is_motion_blur_enabled),
-      ui_task_runner_(base::ThreadTaskRunnerHandle::Get()),
+      ui_task_runner_(base::SingleThreadTaskRunner::GetCurrentDefault()),
       paint_task_runner_(base::ThreadPool::CreateSingleThreadTaskRunner(
           {base::TaskPriority::USER_BLOCKING,
            base::TaskShutdownBehavior::SKIP_ON_SHUTDOWN})),

ash/fast_ink/fast_ink_host.cc

@@ -12,7 +12,7 @@
 
 #include "ash/constants/ash_switches.h"
 #include "base/bind.h"
-#include "base/threading/thread_task_runner_handle.h"
+#include "base/task/single_thread_task_runner.h"
 #include "base/trace_event/trace_event.h"
 #include "cc/base/math_util.h"
 #include "cc/trees/layer_tree_frame_sink.h"
@@ -211,7 +211,8 @@ class FastInkHost::LayerTreeFrameSinkHolder
     if (delete_pending_)
       return;
     delete_pending_ = true;
-    base::ThreadTaskRunnerHandle::Get()->DeleteSoon(FROM_HERE, this);
+    base::SingleThreadTaskRunner::GetCurrentDefault()->DeleteSoon(FROM_HERE,
+                                                                  this);
   }
 
   FastInkHost* host_;
@@ -449,7 +450,7 @@ void FastInkHost::SubmitPendingCompositorFrame() {
 void FastInkHost::DidReceiveCompositorFrameAck() {
   pending_compositor_frame_ack_ = false;
   if (pending_compositor_frame_) {
-    base::ThreadTaskRunnerHandle::Get()->PostTask(
+    base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
         FROM_HERE, base::BindOnce(&FastInkHost::SubmitPendingCompositorFrame,
                                   weak_ptr_factory_.GetWeakPtr()));
   }

ash/fast_ink/laser/laser_pointer_view.cc

@@ -6,7 +6,7 @@
 
 #include "ash/fast_ink/laser/laser_segment_utils.h"
 #include "base/bind.h"
-#include "base/threading/thread_task_runner_handle.h"
+#include "base/task/single_thread_task_runner.h"
 #include "base/trace_event/trace_event.h"
 #include "third_party/skia/include/core/SkColor.h"
 #include "third_party/skia/include/core/SkTypes.h"
@@ -226,7 +226,7 @@ void LaserPointerView::ScheduleUpdateBuffer() {
     return;
 
   pending_update_buffer_ = true;
-  base::ThreadTaskRunnerHandle::Get()->PostTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
       FROM_HERE, base::BindOnce(&LaserPointerView::UpdateBuffer,
                                 weak_ptr_factory_.GetWeakPtr()));
 }

ash/fast_ink/view_tree_host_root_view.cc

@@ -9,7 +9,7 @@
 #include <memory>
 
 #include "base/bind.h"
-#include "base/threading/thread_task_runner_handle.h"
+#include "base/task/single_thread_task_runner.h"
 #include "base/trace_event/trace_event.h"
 #include "cc/paint/display_item_list.h"
 #include "cc/trees/layer_tree_frame_sink.h"
@@ -209,7 +209,8 @@ class ViewTreeHostRootView::LayerTreeViewTreeFrameSinkHolder
     if (delete_pending_)
       return;
     delete_pending_ = true;
-    base::ThreadTaskRunnerHandle::Get()->DeleteSoon(FROM_HERE, this);
+    base::SingleThreadTaskRunner::GetCurrentDefault()->DeleteSoon(FROM_HERE,
+                                                                  this);
   }
 
   ViewTreeHostRootView* view_;
@@ -367,7 +368,7 @@ void ViewTreeHostRootView::SchedulePaintInRect(const gfx::Rect& rect) {
   pending_paint_ = true;
 
   if (!pending_compositor_frame_ack_) {
-    base::ThreadTaskRunnerHandle::Get()->PostTask(
+    base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
         FROM_HERE, base::BindOnce(&ViewTreeHostRootView::Paint,
                                   weak_ptr_factory_.GetWeakPtr()));
   }
@@ -508,7 +509,7 @@ void ViewTreeHostRootView::DidReceiveCompositorFrameAck() {
   pending_compositor_frame_ack_ = false;
 
   if (pending_resource_) {
-    base::ThreadTaskRunnerHandle::Get()->PostTask(
+    base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
         FROM_HERE,
         base::BindOnce(&ViewTreeHostRootView::SubmitPendingCompositorFrame,
                        weak_ptr_factory_.GetWeakPtr()));

ash/highlighter/highlighter_view.cc

@@ -9,7 +9,7 @@
 #include "ash/highlighter/highlighter_gesture_util.h"
 #include "base/bind.h"
 #include "base/memory/ptr_util.h"
-#include "base/threading/thread_task_runner_handle.h"
+#include "base/task/single_thread_task_runner.h"
 #include "base/timer/timer.h"
 #include "base/trace_event/trace_event.h"
 #include "third_party/skia/include/core/SkColor.h"
@@ -207,7 +207,7 @@ void HighlighterView::ScheduleUpdateBuffer() {
     return;
 
   pending_update_buffer_ = true;
-  base::ThreadTaskRunnerHandle::Get()->PostTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
       FROM_HERE, base::BindOnce(&HighlighterView::UpdateBuffer,
                                 weak_ptr_factory_.GetWeakPtr()));
 }

ash/hud_display/graphs_container_view.cc

@@ -11,8 +11,8 @@
 #include "ash/hud_display/hud_constants.h"
 #include "ash/hud_display/memory_graph_page_view.h"
 #include "base/bind.h"
+#include "base/task/single_thread_task_runner.h"
 #include "base/task/thread_pool.h"
-#include "base/threading/thread_task_runner_handle.h"
 #include "ui/base/metadata/metadata_impl_macros.h"
 #include "ui/views/layout/fill_layout.h"
 
@@ -103,7 +103,7 @@ void GraphsContainerView::UpdateData(
   if (next_start_time <= now) {
     RequestDataUpdate();
   } else {
-    base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
+    base::SingleThreadTaskRunner::GetCurrentDefault()->PostDelayedTask(
         FROM_HERE,
         base::BindOnce(&GraphsContainerView::RequestDataUpdate,
                        weak_factory_.GetWeakPtr()),

ash/keyboard/ui/keyboard_ui_controller.cc

@@ -24,7 +24,7 @@
 #include "base/containers/contains.h"
 #include "base/metrics/histogram_functions.h"
 #include "base/metrics/histogram_macros.h"
-#include "base/threading/thread_task_runner_handle.h"
+#include "base/task/single_thread_task_runner.h"
 #include "base/time/time.h"
 #include "base/trace_event/trace_event.h"
 #include "ui/aura/client/aura_constants.h"
@@ -628,7 +628,7 @@ void KeyboardUIController::HideKeyboardImplicitlyBySystem() {
 
   ChangeState(KeyboardUIState::kWillHide);
 
-  base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostDelayedTask(
       FROM_HERE,
       base::BindOnce(&KeyboardUIController::HideKeyboard,
                      weak_factory_will_hide_.GetWeakPtr(),
@@ -955,7 +955,7 @@ void KeyboardUIController::ChangeState(KeyboardUIState state) {
   switch (model_.state()) {
     case KeyboardUIState::kLoading:
     case KeyboardUIState::kWillHide:
-      base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
+      base::SingleThreadTaskRunner::GetCurrentDefault()->PostDelayedTask(
           FROM_HERE,
           base::BindOnce(&KeyboardUIController::ReportLingeringState,
                          weak_factory_report_lingering_state_.GetWeakPtr()),

ash/keyboard/virtual_keyboard_controller.cc

@@ -169,7 +169,7 @@ void VirtualKeyboardController::OnKeyboardHidden(bool is_temporary_hide) {
     return;
 
   // Post a task to reset the virtual keyboard to its original state.
-  base::ThreadTaskRunnerHandle::Get()->PostTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
       FROM_HERE, base::BindOnce(ResetVirtualKeyboard));
 }
 

ash/login/login_screen_controller.cc

@@ -119,7 +119,7 @@ void LoginScreenController::AuthenticateUserWithPasswordOrPin(
       // true.
       LOG(WARNING) << "crbug.com/1339004 : Dummy auth state";
       authentication_stage_ = AuthenticationStage::kDoAuthenticate;
-      base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
+      base::SingleThreadTaskRunner::GetCurrentDefault()->PostDelayedTask(
           FROM_HERE,
           base::BindOnce(&LoginScreenController::OnAuthenticateComplete,
                          weak_factory_.GetWeakPtr(), std::move(callback),

ash/login/ui/lock_screen_media_controls_view.cc

@@ -18,7 +18,7 @@
 #include "base/containers/contains.h"
 #include "base/metrics/histogram_functions.h"
 #include "base/power_monitor/power_monitor.h"
-#include "base/threading/thread_task_runner_handle.h"
+#include "base/task/single_thread_task_runner.h"
 #include "components/media_message_center/media_controls_progress_view.h"
 #include "components/media_message_center/media_notification_util.h"
 #include "components/vector_icons/vector_icons.h"
@@ -252,7 +252,7 @@ LockScreenMediaControlsView::LockScreenMediaControlsView(
           this)) {
     // The system is in the power suspended state. Post OnSuspend call to run
     // after LockContentsView is initialized.
-    base::ThreadTaskRunnerHandle::Get()->PostTask(
+    base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
         FROM_HERE, base::BindOnce(&LockScreenMediaControlsView::OnSuspend,
                                   weak_ptr_factory_.GetWeakPtr()));
   }

ash/login/ui/pin_request_view.cc

@@ -534,7 +534,7 @@ void PinRequestView::OnInputChange(bool last_field_active, bool complete) {
 
     // Moving focus is delayed by using PostTask to allow for proper
     // a11y announcements.
-    base::ThreadTaskRunnerHandle::Get()->PostTask(
+    base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
         FROM_HERE, base::BindOnce(&PinRequestView::FocusSubmitButton,
                                   weak_ptr_factory_.GetWeakPtr()));
   }

ash/metrics/login_unlock_throughput_recorder_unittest.cc

@@ -199,7 +199,7 @@ void GiveItSomeTime(base::TimeDelta delta) {
   base::RunLoop run_loop(base::RunLoop::Type::kNestableTasksAllowed);
   auto* compositor = Shell::GetPrimaryRootWindow()->GetHost()->compositor();
   compositor->ScheduleFullRedraw();
-  base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostDelayedTask(
       FROM_HERE, run_loop.QuitClosure(), delta);
   run_loop.Run();
 }

ash/projector/projector_ui_controller_unittest.cc

@@ -253,7 +253,7 @@ TEST_F(ProjectorUiControllerTest, LongPressShowsBubble) {
 
   // Hold the press down for 2 ms, to trigger a long press.
   base::RunLoop run_loop;
-  base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostDelayedTask(
       FROM_HERE, run_loop.QuitClosure(), base::Milliseconds(2));
   run_loop.Run();
 

ash/public/cpp/pagination/pagination_model_unittest.cc

@@ -175,7 +175,7 @@ class PaginationModelTest : public views::test::WidgetTest {
   void WaitForRevertAnimation() {
     while (pagination()->IsRevertingCurrentTransition()) {
       base::RunLoop run_loop;
-      base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
+      base::SingleThreadTaskRunner::GetCurrentDefault()->PostDelayedTask(
           FROM_HERE, run_loop.QuitClosure(), base::Milliseconds(100));
       run_loop.Run();
     }

ash/quick_pair/keyed_service/quick_pair_mediator.cc

@@ -30,7 +30,7 @@
 #include "ash/quick_pair/scanning/scanner_broker_impl.h"
 #include "ash/quick_pair/ui/actions.h"
 #include "ash/quick_pair/ui/ui_broker_impl.h"
-#include "base/threading/thread_task_runner_handle.h"
+#include "base/task/single_thread_task_runner.h"
 #include "chromeos/ash/services/bluetooth_config/fast_pair_delegate.h"
 #include "chromeos/ash/services/quick_pair/quick_pair_process.h"
 #include "chromeos/ash/services/quick_pair/quick_pair_process_manager_impl.h"
@@ -111,7 +111,7 @@ Mediator::Mediator(
 
   // Asynchronously bind to CrosBluetoothConfig so that we don't attempt to
   // bind to it before it has initialized.
-  base::ThreadTaskRunnerHandle::Get()->PostTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
       FROM_HERE, base::BindOnce(&Mediator::BindToCrosBluetoothConfig,
                                 weak_ptr_factory_.GetWeakPtr()));
 }

ash/root_window_controller.cc

@@ -669,8 +669,8 @@ void RootWindowController::Shutdown() {
 
   // The targeter may still on the stack, so delete it later.
   if (targeter) {
-    base::ThreadTaskRunnerHandle::Get()->DeleteSoon(FROM_HERE,
-                                                    std::move(targeter));
+    base::SingleThreadTaskRunner::GetCurrentDefault()->DeleteSoon(
+        FROM_HERE, std::move(targeter));
   }
 }
 

ash/session/session_controller_impl_unittest.cc

@@ -21,8 +21,8 @@
 #include "base/bind.h"
 #include "base/callback.h"
 #include "base/run_loop.h"
+#include "base/task/single_thread_task_runner.h"
 #include "base/test/bind.h"
-#include "base/threading/thread_task_runner_handle.h"
 #include "components/prefs/testing_pref_service.h"
 #include "components/user_manager/user_type.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ -671,7 +671,7 @@ class CanSwitchUserTest : public AshTestBase {
   // The passed |action| type parameter defines the outcome (which will be
   // checked) and the action the user will choose.
   void SwitchUser(ActionType action) {
-    base::ThreadTaskRunnerHandle::Get()->PostTask(
+    base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
         FROM_HERE, base::BindOnce(&CloseMessageBox, action));
     Shell::Get()->session_controller()->CanSwitchActiveUser(base::BindOnce(
         &CanSwitchUserTest::SwitchCallback, base::Unretained(this)));

ash/session/test_session_controller_client.cc

@@ -17,7 +17,7 @@
 #include "base/ranges/algorithm.h"
 #include "base/run_loop.h"
 #include "base/strings/stringprintf.h"
-#include "base/threading/thread_task_runner_handle.h"
+#include "base/task/single_thread_task_runner.h"
 #include "components/account_id/account_id.h"
 #include "components/prefs/pref_service.h"
 #include "components/session_manager/session_manager_types.h"
@@ -221,7 +221,7 @@ void TestSessionControllerClient::RequestLockScreen() {
     Shell::Get()->login_screen_controller()->ShowLockScreen();
   }
 
-  base::ThreadTaskRunnerHandle::Get()->PostTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
       FROM_HERE, base::BindOnce(&TestSessionControllerClient::SetSessionState,
                                 weak_ptr_factory_.GetWeakPtr(),
                                 session_manager::SessionState::LOCKED));

ash/shelf/hotseat_widget_unittest.cc

@@ -467,7 +467,7 @@ TEST_P(HotseatWidgetTest, InAppShelfShowingContextMenu) {
   const int long_press_delay_ms = gesture_config->long_press_time_in_ms() +
                                   gesture_config->show_press_delay_in_ms();
   base::RunLoop run_loop;
-  base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostDelayedTask(
       FROM_HERE, run_loop.QuitClosure(),
       base::Milliseconds(long_press_delay_ms));
   run_loop.Run();

ash/shelf/login_shelf_view.cc

@@ -43,7 +43,7 @@
 #include "base/callback_helpers.h"
 #include "base/metrics/user_metrics.h"
 #include "base/sequence_checker.h"
-#include "base/threading/thread_task_runner_handle.h"
+#include "base/task/single_thread_task_runner.h"
 #include "chromeos/strings/grit/chromeos_strings.h"
 #include "chromeos/ui/vector_icons/vector_icons.h"
 #include "skia/ext/image_operations.h"
@@ -556,7 +556,7 @@ LoginShelfView::LoginShelfView(
   add_button(kParentAccess, base::BindRepeating([]() {
                // TODO(https://crbug.com/999387): Remove this when handling
                // touch cancellation is fixed for system modal windows.
-               base::ThreadTaskRunnerHandle::Get()->PostTask(
+               base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
                    FROM_HERE, base::BindOnce([]() {
                      LockScreen::Get()->ShowParentAccessDialog();
                    }));

ash/shelf/shelf_layout_manager.cc

@@ -1331,7 +1331,7 @@ void ShelfLayoutManager::LockAutoHideState(bool lock_auto_hide_state) {
   // If unlocking, recompute the current state, but do it after the current
   // event is processed.
   if (!is_auto_hide_state_locked_) {
-    base::ThreadTaskRunnerHandle::Get()->PostTask(
+    base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
         FROM_HERE, base::BindOnce(&ShelfLayoutManager::UpdateAutoHideState,
                                   weak_factory_.GetWeakPtr()));
   }
@@ -3002,7 +3002,7 @@ void ShelfLayoutManager::OnShelfTrayBubbleVisibilityChanged(bool bubble_shown) {
   // created/destructed. Meanwhile, we rely on the state of tray bubble to
   // calculate the auto-hide state.
   // Use ThreadTaskRunnerHandle to specify that the task runs on the UI thread.
-  base::ThreadTaskRunnerHandle::Get()->PostTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
       FROM_HERE, visibility_update_for_tray_callback_.callback());
 }
 

ash/shelf/shelf_unittest.cc

@@ -23,7 +23,7 @@
 #include "base/bind.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/stringprintf.h"
-#include "base/threading/thread_task_runner_handle.h"
+#include "base/task/single_thread_task_runner.h"
 #include "components/session_manager/session_manager_types.h"
 #include "ui/aura/client/aura_constants.h"
 #include "ui/wm/core/window_util.h"
@@ -167,7 +167,7 @@ TEST_F(NoSessionShelfTest, SetAlignmentDuringDisplayDisconnect) {
   base::RunLoop().RunUntilIdle();
 
   // The task indirectly triggers Shelf::SetAlignment() via a SessionObserver.
-  base::ThreadTaskRunnerHandle::Get()->PostTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
       FROM_HERE,
       base::BindOnce(
           [](TestSessionControllerClient* session) {

ash/shelf/shelf_view.cc

@@ -726,7 +726,7 @@ void ShelfView::ButtonPressed(views::Button* sender,
   scoped_display_for_new_windows_ =
       std::make_unique<display::ScopedDisplayForNewWindows>(
           window->GetRootWindow());
-  base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostDelayedTask(
       FROM_HERE,
       base::BindOnce(&ShelfView::DestroyScopedDisplay,
                      weak_factory_.GetWeakPtr()),

ash/shortcut_viewer/views/keyboard_shortcut_view.cc

@@ -358,7 +358,7 @@ void KeyboardShortcutView::OnPaint(gfx::Canvas* canvas) {
   // compositor. We can wait for the second OnPaint, which means previous
   // drawing commands have been sent to compositor for the next frame and new
   // coming commands will be sent for the next-next frame.
-  base::ThreadTaskRunnerHandle::Get()->PostTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
       FROM_HERE, base::BindOnce(&KeyboardShortcutView::InitCategoriesTabbedPane,
                                 weak_factory_.GetWeakPtr(), kAllCategories));
 }

ash/system/bluetooth/bluetooth_device_status_ui_handler.cc

@@ -11,7 +11,7 @@
 #include "ash/strings/grit/ash_strings.h"
 #include "base/bind.h"
 #include "base/check.h"
-#include "base/threading/thread_task_runner_handle.h"
+#include "base/task/single_thread_task_runner.h"
 #include "chromeos/ash/services/bluetooth_config/public/cpp/cros_bluetooth_config_util.h"
 #include "device/bluetooth/chromeos/bluetooth_utils.h"
 #include "ui/base/l10n/l10n_util.h"
@@ -30,7 +30,7 @@ const char kBluetoothToastIdPrefix[] = "cros_bluetooth_device_toast_id-";
 BluetoothDeviceStatusUiHandler::BluetoothDeviceStatusUiHandler() {
   // Asynchronously bind to CrosBluetoothConfig so that we don't want to attempt
   // to bind to it before it has initialized.
-  base::ThreadTaskRunnerHandle::Get()->PostTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
       FROM_HERE,
       base::BindOnce(&BluetoothDeviceStatusUiHandler::BindToCrosBluetoothConfig,
                      weak_ptr_factory_.GetWeakPtr()));

ash/system/power/power_event_observer.cc

@@ -21,7 +21,7 @@
 #include "base/bind.h"
 #include "base/location.h"
 #include "base/scoped_multi_source_observation.h"
-#include "base/threading/thread_task_runner_handle.h"
+#include "base/task/single_thread_task_runner.h"
 #include "chromeos/ash/components/feature_usage/feature_usage_metrics.h"
 #include "ui/aura/window.h"
 #include "ui/aura/window_tree_host.h"
@@ -174,7 +174,7 @@ class CompositorWatcher : public ui::CompositorObserver {
 
     // Post task to make sure callback is not invoked synchronously as watcher
     // is started.
-    base::ThreadTaskRunnerHandle::Get()->PostTask(
+    base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
         FROM_HERE,
         base::BindOnce(&CompositorWatcher::RunCallbackIfAllCompositingEnded,
                        weak_ptr_factory_.GetWeakPtr()));

ash/system/time/calendar_unittest_utils.cc

@@ -98,7 +98,7 @@ base::OnceClosure CalendarClientTestImpl::GetEventList(
   // little longer than the settle down duration, so in the test after the
   // animation settled down it can still be with `kFetching` status until
   // somemethod like `WaitUntilFetched` is called.
-  base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostDelayedTask(
       FROM_HERE,
       base::BindOnce(std::move(callback), error_, std::move(events_)),
       task_delay_);

ash/system/toast/toast_manager_unittest.cc

@@ -69,7 +69,7 @@ void WaitForAnimationEnded(ui::Layer* layer) {
 // Waits for a time delta `time`.
 void WaitForTimeDelta(base::TimeDelta time) {
   base::RunLoop run_loop;
-  base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostDelayedTask(
       FROM_HERE, run_loop.QuitClosure(), time);
   run_loop.Run();
 }
@@ -982,7 +982,7 @@ TEST_F(ToastManagerImplTest, ShowAndCloseToastsOnAllRootWindows) {
       }
       case CancellationSource::kToastDuration: {
         base::RunLoop run_loop;
-        base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
+        base::SingleThreadTaskRunner::GetCurrentDefault()->PostDelayedTask(
             FROM_HERE, run_loop.QuitClosure(),
             ToastData::kDefaultToastDuration);
         run_loop.Run();

ash/test/ash_test_base.cc

@@ -40,8 +40,8 @@
 #include "base/memory/ptr_util.h"
 #include "base/run_loop.h"
 #include "base/strings/strcat.h"
+#include "base/task/single_thread_task_runner.h"
 #include "base/task/thread_pool/thread_pool_instance.h"
-#include "base/threading/thread_task_runner_handle.h"
 #include "chromeos/dbus/power/fake_power_manager_client.h"
 #include "components/account_id/account_id.h"
 #include "components/user_manager/user_names.h"
@@ -127,7 +127,7 @@ void AshTestBase::SetUp() {
 void AshTestBase::SetUp(std::unique_ptr<TestShellDelegate> delegate) {
   // At this point, the task APIs should already be provided by
   // |task_environment_|.
-  CHECK(base::ThreadTaskRunnerHandle::IsSet());
+  CHECK(base::SingleThreadTaskRunner::HasCurrentDefault());
   CHECK(base::ThreadPoolInstance::Get());
 
   setup_called_ = true;

ash/test/ash_test_util.cc

@@ -53,7 +53,7 @@ bool TakePrimaryDisplayScreenshotAndSave(const base::FilePath& file_path) {
 
 void GiveItSomeTimeForDebugging(base::TimeDelta time_duration) {
   base::RunLoop run_loop;
-  base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostDelayedTask(
       FROM_HERE, run_loop.QuitClosure(), time_duration);
   run_loop.Run();
 }

ash/test/ash_test_views_delegate.cc

@@ -38,7 +38,7 @@ views::TestViewsDelegate::ProcessMenuAcceleratorResult
 AshTestViewsDelegate::ProcessAcceleratorWhileMenuShowing(
     const ui::Accelerator& accelerator) {
   if (ash::AcceleratorController::Get()->OnMenuAccelerator(accelerator)) {
-    base::ThreadTaskRunnerHandle::Get()->PostTask(
+    base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
         FROM_HERE, base::BindOnce(ProcessAcceleratorNow, accelerator));
     return views::ViewsDelegate::ProcessMenuAcceleratorResult::CLOSE_MENU;
   }

ash/webui/camera_app_ui/document_scanner_installer.cc

@@ -7,7 +7,7 @@
 #include "ash/webui/camera_app_ui/document_scanner_service_client.h"
 #include "base/callback_helpers.h"
 #include "base/logging.h"
-#include "base/threading/thread_task_runner_handle.h"
+#include "base/task/single_thread_task_runner.h"
 
 namespace ash {
 
@@ -62,7 +62,7 @@ void DocumentScannerInstaller::TriggerInstall() {
 }
 
 DocumentScannerInstaller::DocumentScannerInstaller()
-    : ui_task_runner_(base::ThreadTaskRunnerHandle::Get()) {}
+    : ui_task_runner_(base::SingleThreadTaskRunner::GetCurrentDefault()) {}
 
 void DocumentScannerInstaller::OnInstalled(
     const DlcserviceClient::InstallResult& install_result) {

ash/wm/desks/desks_controller.cc

@@ -1856,7 +1856,7 @@ void DesksController::FinalizeDeskRemoval(RemovedDeskData* removed_desk_data) {
 
   // Schedules a delayed task to forcefully close all windows that have not
   // finish closing.
-  base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostDelayedTask(
       FROM_HERE,
       base::BindOnce(&DesksController::CleanUpClosedAppWindowsTask,
                      weak_ptr_factory_.GetWeakPtr(),

ash/wm/desks/desks_test_util.cc

@@ -180,7 +180,7 @@ bool GetDeskActionVisibilityForMiniView(const DeskMiniView* mini_view) {
 
 void WaitForMilliseconds(int milliseconds) {
   base::RunLoop run_loop;
-  base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostDelayedTask(
       FROM_HERE, run_loop.QuitClosure(), base::Milliseconds(milliseconds));
   run_loop.Run();
 }

ash/wm/desks/desks_textfield.cc

@@ -169,7 +169,7 @@ void DesksTextfield::OnBlur() {
   // still being activated. In this case, we want to set the stored focus view
   // to nullptr after the stack of the call to `FocusManager::ClearFocus()`
   // returns completely.
-  base::ThreadTaskRunnerHandle::Get()->PostTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
       FROM_HERE, base::BindOnce(
                      [](base::WeakPtr<views::Widget> w) {
                        if (w)

ash/wm/desks/templates/saved_desk_item_view.cc

@@ -540,7 +540,7 @@ void SavedDeskItemView::OnViewBlurred(views::View* observed_view) {
       saved_desk_util::GetSavedDeskPresenter()->FindOtherEntryWithName(
           name_view_->GetText(), desk_template().type(), uuid());
   if (template_to_replace) {
-    base::ThreadTaskRunnerHandle::Get()->PostTask(
+    base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
         FROM_HERE, base::BindOnce(&SavedDeskItemView::MaybeShowReplaceDialog,
                                   weak_ptr_factory_.GetWeakPtr(),
                                   template_to_replace->type(),

ash/wm/gestures/back_gesture/back_gesture_contextual_nudge_controller_impl_unittest.cc

@@ -97,7 +97,7 @@ class BackGestureContextualNudgeControllerTest : public NoSessionAshTestBase {
   void WaitNudgeAnimationDone() {
     while (nudge()) {
       base::RunLoop run_loop;
-      base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
+      base::SingleThreadTaskRunner::GetCurrentDefault()->PostDelayedTask(
           FROM_HERE, run_loop.QuitClosure(), base::Milliseconds(100));
       run_loop.Run();
     }

ash/wm/overview/delayed_animation_observer_impl.cc

@@ -6,12 +6,12 @@
 
 #include "ash/wm/overview/overview_delegate.h"
 #include "base/bind.h"
-#include "base/threading/thread_task_runner_handle.h"
+#include "base/task/single_thread_task_runner.h"
 
 namespace ash {
 
 ForceDelayObserver::ForceDelayObserver(base::TimeDelta delay) {
-  base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostDelayedTask(
       FROM_HERE,
       base::BindOnce(&ForceDelayObserver::Finish,
                      weak_ptr_factory_.GetWeakPtr()),

ash/wm/overview/overview_controller.cc

@@ -31,7 +31,7 @@
 #include "base/containers/unique_ptr_adapters.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/ranges/algorithm.h"
-#include "base/threading/thread_task_runner_handle.h"
+#include "base/task/single_thread_task_runner.h"
 #include "base/trace_event/trace_event.h"
 #include "ui/views/widget/widget.h"
 #include "ui/wm/core/window_util.h"
@@ -191,7 +191,7 @@ void OverviewController::PauseOcclusionTracker() {
 void OverviewController::UnpauseOcclusionTracker(base::TimeDelta delay) {
   reset_pauser_task_.Reset(base::BindOnce(&OverviewController::ResetPauser,
                                           weak_ptr_factory_.GetWeakPtr()));
-  base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostDelayedTask(
       FROM_HERE, reset_pauser_task_.callback(), delay);
 }
 
@@ -204,7 +204,7 @@ void OverviewController::RemoveObserver(OverviewObserver* observer) {
 }
 
 void OverviewController::DelayedUpdateRoundedCornersAndShadow() {
-  base::ThreadTaskRunnerHandle::Get()->PostTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
       FROM_HERE,
       base::BindOnce(&OverviewController::UpdateRoundedCornersAndShadow,
                      weak_ptr_factory_.GetWeakPtr()));
@@ -362,7 +362,7 @@ void OverviewController::ToggleOverview(OverviewEnterExitType type) {
     }
 
     // Don't delete |overview_session_| yet since the stack is still using it.
-    base::ThreadTaskRunnerHandle::Get()->DeleteSoon(
+    base::SingleThreadTaskRunner::GetCurrentDefault()->DeleteSoon(
         FROM_HERE, overview_session_.release());
     last_overview_session_time_ = base::Time::Now();
     for (auto& observer : observers_)

ash/wm/overview/overview_session.cc

@@ -55,7 +55,7 @@
 #include "base/metrics/histogram_macros.h"
 #include "base/metrics/user_metrics.h"
 #include "base/ranges/algorithm.h"
-#include "base/threading/thread_task_runner_handle.h"
+#include "base/task/single_thread_task_runner.h"
 #include "ui/accessibility/ax_enums.mojom.h"
 #include "ui/base/hit_test.h"
 #include "ui/base/l10n/l10n_util.h"
@@ -161,7 +161,7 @@ OverviewSession::~OverviewSession() {
   // using it.
   if (window_drag_controller_) {
     window_drag_controller_->ResetOverviewSession();
-    base::ThreadTaskRunnerHandle::Get()->DeleteSoon(
+    base::SingleThreadTaskRunner::GetCurrentDefault()->DeleteSoon(
         FROM_HERE, window_drag_controller_.release());
   }
 }

ash/wm/overview/overview_session_unittest.cc

@@ -4628,7 +4628,7 @@ TEST_F(SplitViewOverviewSessionTest, OverviewDragControllerBehavior) {
 
   // Simulate a long press, which is required to snap windows.
   base::RunLoop run_loop;
-  base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostDelayedTask(
       FROM_HERE, run_loop.QuitClosure(), base::Milliseconds(2));
   run_loop.Run();
 
@@ -5593,7 +5593,7 @@ TEST_F(SplitViewOverviewSessionTest,
   generator->PressTouch();
   {
     base::RunLoop run_loop;
-    base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
+    base::SingleThreadTaskRunner::GetCurrentDefault()->PostDelayedTask(
         FROM_HERE, run_loop.QuitClosure(), base::Milliseconds(2));
     run_loop.Run();
   }
@@ -5615,7 +5615,7 @@ TEST_F(SplitViewOverviewSessionTest,
   generator->PressTouch();
   {
     base::RunLoop run_loop;
-    base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
+    base::SingleThreadTaskRunner::GetCurrentDefault()->PostDelayedTask(
         FROM_HERE, run_loop.QuitClosure(), base::Milliseconds(2));
     run_loop.Run();
   }

ash/wm/overview/overview_window_drag_histogram_unittests.cc

@@ -21,9 +21,9 @@
 #include "ash/wm/tablet_mode/tablet_mode_controller_test_api.h"
 #include "base/location.h"
 #include "base/run_loop.h"
+#include "base/task/single_thread_task_runner.h"
 #include "base/test/metrics/histogram_tester.h"
 #include "base/test/scoped_feature_list.h"
-#include "base/threading/thread_task_runner_handle.h"
 #include "base/time/time.h"
 #include "ui/aura/window.h"
 #include "ui/display/display.h"
@@ -108,7 +108,7 @@ class OverviewWindowDragHistogramTest : public AshTestBase {
         EnterOverviewAndGetItemCenterPoint());
     generator->PressTouch();
     base::RunLoop run_loop;
-    base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
+    base::SingleThreadTaskRunner::GetCurrentDefault()->PostDelayedTask(
         FROM_HERE, run_loop.QuitClosure(), base::Milliseconds(2));
     run_loop.Run();
 

ash/wm/overview/scoped_overview_transform_window.cc

@@ -25,7 +25,6 @@
 #include "ash/wm/window_util.h"
 #include "base/bind.h"
 #include "base/task/single_thread_task_runner.h"
-#include "base/threading/thread_task_runner_handle.h"
 #include "chromeos/ui/base/window_properties.h"
 #include "ui/aura/client/aura_constants.h"
 #include "ui/aura/client/transient_window_client.h"
@@ -499,7 +498,7 @@ void ScopedOverviewTransformWindow::Close() {
     return;
   }
 
-  base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostDelayedTask(
       FROM_HERE,
       base::BindOnce(&ScopedOverviewTransformWindow::CloseWidget,
                      weak_ptr_factory_.GetWeakPtr()),

ash/wm/toplevel_window_event_handler_unittest.cc

@@ -29,7 +29,7 @@
 #include "base/bind.h"
 #include "base/compiler_specific.h"
 #include "base/run_loop.h"
-#include "base/threading/thread_task_runner_handle.h"
+#include "base/task/single_thread_task_runner.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "ui/aura/client/aura_constants.h"
 #include "ui/aura/client/capture_client.h"
@@ -189,7 +189,7 @@ TEST_F(ToplevelWindowEventHandlerTest, WindowPositionAutoManagement) {
   generator.PressLeftButton();
   ::wm::WindowMoveClient* move_client =
       ::wm::GetWindowMoveClient(w1->GetRootWindow());
-  base::ThreadTaskRunnerHandle::Get()->PostTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
       FROM_HERE,
       base::BindOnce(&ContinueAndCompleteDrag, base::Unretained(&generator),
                      base::Unretained(window_state),
@@ -208,7 +208,7 @@ TEST_F(ToplevelWindowEventHandlerTest, WindowPositionAutoManagement) {
   // restored after drag completes.
   window_state->SetWindowPositionManaged(false);
   generator.PressLeftButton();
-  base::ThreadTaskRunnerHandle::Get()->PostTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
       FROM_HERE,
       base::BindOnce(&ContinueAndCompleteDrag, base::Unretained(&generator),
                      base::Unretained(window_state),
@@ -1030,7 +1030,7 @@ TEST_F(ToplevelWindowEventHandlerTest, CaptureLossAfterMouseRelease) {
 
   ::wm::WindowMoveClient* move_client =
       ::wm::GetWindowMoveClient(window->GetRootWindow());
-  base::ThreadTaskRunnerHandle::Get()->PostTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
       FROM_HERE, base::BindOnce(&SendMouseReleaseAndReleaseCapture,
                                 base::Unretained(&generator),
                                 base::Unretained(window.get())));
@@ -1057,7 +1057,7 @@ TEST_F(ToplevelWindowEventHandlerTest, GestureDragCaptureLoss) {
 
   ::wm::WindowMoveClient* move_client =
       ::wm::GetWindowMoveClient(window->GetRootWindow());
-  base::ThreadTaskRunnerHandle::Get()->PostTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
       FROM_HERE, base::BindOnce(&CheckHasCaptureAndReleaseCapture,
                                 base::Unretained(window.get())));
   EXPECT_EQ(::wm::MOVE_SUCCESSFUL,

ash/wm/video_detector.cc

@@ -128,7 +128,7 @@ void VideoDetector::EstablishConnectionToViz() {
 void VideoDetector::OnConnectionError() {
   if (video_is_playing_)
     OnVideoActivityEnded();
-  base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostDelayedTask(
       FROM_HERE,
       base::BindOnce(&VideoDetector::EstablishConnectionToViz,
                      weak_factory_.GetWeakPtr()),

ash/wm/window_animations_unittest.cc

@@ -34,7 +34,7 @@ namespace {
 
 void WaitForMilliseconds(int ms) {
   base::RunLoop loop;
-  base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostDelayedTask(
       FROM_HERE, loop.QuitClosure(), base::Milliseconds(ms));
   loop.Run();
 }

ash/wm/window_restore/window_restore_controller.cc

@@ -27,7 +27,7 @@
 #include "base/check_op.h"
 #include "base/containers/adapters.h"
 #include "base/containers/contains.h"
-#include "base/threading/thread_task_runner_handle.h"
+#include "base/task/single_thread_task_runner.h"
 #include "components/account_id/account_id.h"
 #include "components/app_restore/app_restore_info.h"
 #include "components/app_restore/full_restore_utils.h"
@@ -360,7 +360,7 @@ void WindowRestoreController::OnWindowPropertyChanged(aura::Window* window,
     restore_property_clear_callbacks_.emplace(
         window, base::BindOnce(&WindowRestoreController::ClearLaunchedKey,
                                weak_ptr_factory_.GetWeakPtr(), window));
-    base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
+    base::SingleThreadTaskRunner::GetCurrentDefault()->PostDelayedTask(
         FROM_HERE, restore_property_clear_callbacks_[window].callback(),
         kAllowActivationDelay);
   }
@@ -569,7 +569,7 @@ void WindowRestoreController::RestoreStateTypeAndClearLaunchedKey(
               (app_type == AppType::ARC_APP && is_real_arc_window)
           ? kAllowActivationDelay
           : base::TimeDelta();
-  base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostDelayedTask(
       FROM_HERE, restore_property_clear_callbacks_[window].callback(), delay);
 }
 

ash/wm/workspace/workspace_event_handler_unittest.cc

@@ -14,7 +14,7 @@
 #include "ash/wm/workspace_controller_test_api.h"
 #include "base/containers/contains.h"
 #include "base/run_loop.h"
-#include "base/threading/thread_task_runner_handle.h"
+#include "base/task/single_thread_task_runner.h"
 #include "ui/aura/client/aura_constants.h"
 #include "ui/aura/test/test_window_delegate.h"
 #include "ui/aura/window.h"
@@ -547,7 +547,8 @@ TEST_F(WorkspaceEventHandlerTest, DeleteWhileInRunLoop) {
   delegate.set_window_component(HTCAPTION);
 
   ASSERT_TRUE(::wm::GetWindowMoveClient(window->GetRootWindow()));
-  base::ThreadTaskRunnerHandle::Get()->DeleteSoon(FROM_HERE, window.get());
+  base::SingleThreadTaskRunner::GetCurrentDefault()->DeleteSoon(FROM_HERE,
+                                                                window.get());
   ::wm::GetWindowMoveClient(window->GetRootWindow())
       ->RunMoveLoop(window.release(), gfx::Vector2d(),
                     ::wm::WINDOW_MOVE_SOURCE_MOUSE);

cc/animation/animation_host_perftest.cc

@@ -5,7 +5,7 @@
 #include "base/memory/raw_ptr.h"
 #include "cc/animation/animation_host.h"
 
-#include "base/threading/thread_task_runner_handle.h"
+#include "base/task/single_thread_task_runner.h"
 #include "base/timer/lap_timer.h"
 #include "cc/animation/animation.h"
 #include "cc/animation/animation_id_provider.h"
@@ -36,7 +36,8 @@ class AnimationHostPerfTest : public testing::Test {
     layer_tree_host_ = FakeLayerTreeHost::Create(
         &fake_client_, &task_graph_runner_, animation_host_.get(), settings);
     layer_tree_host_->InitializeSingleThreaded(
-        &single_thread_client_, base::ThreadTaskRunnerHandle::Get());
+        &single_thread_client_,
+        base::SingleThreadTaskRunner::GetCurrentDefault());
 
     root_layer_ = Layer::Create();
     layer_tree_host_->SetRootLayer(root_layer_);

cc/base/unique_notifier_unittest.cc

@@ -7,7 +7,6 @@
 #include "base/callback_helpers.h"
 #include "base/run_loop.h"
 #include "base/task/single_thread_task_runner.h"
-#include "base/threading/thread_task_runner_handle.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace cc {
@@ -49,9 +48,10 @@ class UniqueNotifierTest : public testing::Test {
 // 50000 can be any number bigger than 1. The bigger the easier to more runs.
 TEST_F(UniqueNotifierTest, Schedule) {
   {
-    UniqueNotifier notifier(base::ThreadTaskRunnerHandle::Get().get(),
-                            base::BindRepeating(&UniqueNotifierTest::Notify,
-                                                base::Unretained(this)));
+    UniqueNotifier notifier(
+        base::SingleThreadTaskRunner::GetCurrentDefault().get(),
+        base::BindRepeating(&UniqueNotifierTest::Notify,
+                            base::Unretained(this)));
 
     EXPECT_EQ(0, NotificationCount());
 

cc/benchmarks/micro_benchmark_controller.cc

@@ -10,7 +10,7 @@
 #include "base/callback.h"
 #include "base/containers/cxx20_erase.h"
 #include "base/ranges/algorithm.h"
-#include "base/threading/thread_task_runner_handle.h"
+#include "base/task/single_thread_task_runner.h"
 #include "base/values.h"
 #include "cc/benchmarks/invalidation_benchmark.h"
 #include "cc/benchmarks/rasterize_and_record_benchmark.h"
@@ -45,9 +45,10 @@ std::unique_ptr<MicroBenchmark> CreateBenchmark(
 
 MicroBenchmarkController::MicroBenchmarkController(LayerTreeHost* host)
     : host_(host),
-      main_controller_task_runner_(base::ThreadTaskRunnerHandle::IsSet()
-                                       ? base::ThreadTaskRunnerHandle::Get()
-                                       : nullptr) {
+      main_controller_task_runner_(
+          base::SingleThreadTaskRunner::HasCurrentDefault()
+              ? base::SingleThreadTaskRunner::GetCurrentDefault()
+              : nullptr) {
   DCHECK(host_);
 }
 

cc/benchmarks/micro_benchmark_controller_unittest.cc

@@ -37,8 +37,8 @@ class MicroBenchmarkControllerTest : public testing::Test {
         &layer_tree_host_client_, &task_graph_runner_, animation_host_.get());
     layer_tree_host_->SetRootLayer(Layer::Create());
     layer_tree_host_->InitializeForTesting(
-        TaskRunnerProvider::Create(base::ThreadTaskRunnerHandle::Get(),
-                                   nullptr),
+        TaskRunnerProvider::Create(
+            base::SingleThreadTaskRunner::GetCurrentDefault(), nullptr),
         std::unique_ptr<Proxy>(new FakeProxy));
   }
 

cc/layers/layer_perftest.cc

@@ -4,7 +4,7 @@
 
 #include "cc/layers/layer.h"
 
-#include "base/threading/thread_task_runner_handle.h"
+#include "base/task/single_thread_task_runner.h"
 #include "base/timer/lap_timer.h"
 #include "cc/animation/animation_host.h"
 #include "cc/test/fake_impl_task_runner_provider.h"
@@ -37,7 +37,8 @@ class LayerPerfTest : public testing::Test {
     layer_tree_host_ = FakeLayerTreeHost::Create(
         &fake_client_, &task_graph_runner_, animation_host_.get());
     layer_tree_host_->InitializeSingleThreaded(
-        &single_thread_client_, base::ThreadTaskRunnerHandle::Get());
+        &single_thread_client_,
+        base::SingleThreadTaskRunner::GetCurrentDefault());
   }
 
   void TearDown() override {

cc/layers/layer_unittest.cc

@@ -11,7 +11,7 @@
 
 #include "base/bind.h"
 #include "base/containers/contains.h"
-#include "base/threading/thread_task_runner_handle.h"
+#include "base/task/single_thread_task_runner.h"
 #include "cc/animation/animation_host.h"
 #include "cc/animation/animation_id_provider.h"
 #include "cc/base/math_util.h"
@@ -117,7 +117,7 @@ class MockLayerTreeHost : public LayerTreeHost {
                     LayerTreeHost::InitParams params)
       : LayerTreeHost(std::move(params), CompositorMode::SINGLE_THREADED) {
     InitializeSingleThreaded(single_thread_client,
-                             base::ThreadTaskRunnerHandle::Get());
+                             base::SingleThreadTaskRunner::GetCurrentDefault());
   }
 
   CommitState* GetPendingCommitState() { return pending_commit_state(); }
@@ -1191,7 +1191,7 @@ class LayerTreeHostFactory {
     params.client = &client_;
     params.task_graph_runner = &task_graph_runner_;
     params.settings = &settings;
-    params.main_task_runner = base::ThreadTaskRunnerHandle::Get();
+    params.main_task_runner = base::SingleThreadTaskRunner::GetCurrentDefault();
     params.mutator_host = mutator_host;
 
     return LayerTreeHost::CreateSingleThreaded(&single_thread_client_,

cc/layers/picture_layer_unittest.cc

@@ -8,7 +8,7 @@
 
 #include <utility>
 
-#include "base/threading/thread_task_runner_handle.h"
+#include "base/task/single_thread_task_runner.h"
 #include "cc/animation/animation_host.h"
 #include "cc/base/completion_event.h"
 #include "cc/layers/append_quads_data.h"
@@ -266,7 +266,7 @@ TEST(PictureLayerTest, NonMonotonicSourceFrameNumber) {
   params.client = &host_client1;
   params.settings = &settings;
   params.task_graph_runner = &task_graph_runner;
-  params.main_task_runner = base::ThreadTaskRunnerHandle::Get();
+  params.main_task_runner = base::SingleThreadTaskRunner::GetCurrentDefault();
   params.mutator_host = animation_host.get();
   std::unique_ptr<LayerTreeHost> host1 = LayerTreeHost::CreateSingleThreaded(
       &single_thread_client, std::move(params));
@@ -279,7 +279,7 @@ TEST(PictureLayerTest, NonMonotonicSourceFrameNumber) {
   params2.client = &host_client1;
   params2.settings = &settings;
   params2.task_graph_runner = &task_graph_runner;
-  params2.main_task_runner = base::ThreadTaskRunnerHandle::Get();
+  params2.main_task_runner = base::SingleThreadTaskRunner::GetCurrentDefault();
   params2.client = &host_client2;
   params2.mutator_host = animation_host2.get();
   std::unique_ptr<LayerTreeHost> host2 = LayerTreeHost::CreateSingleThreaded(
@@ -338,7 +338,7 @@ TEST(PictureLayerTest, ChangingHostsWithCollidingFrames) {
   params.client = &host_client1;
   params.settings = &settings;
   params.task_graph_runner = &task_graph_runner;
-  params.main_task_runner = base::ThreadTaskRunnerHandle::Get();
+  params.main_task_runner = base::SingleThreadTaskRunner::GetCurrentDefault();
   params.mutator_host = animation_host.get();
   std::unique_ptr<LayerTreeHost> host1 = LayerTreeHost::CreateSingleThreaded(
       &single_thread_client, std::move(params));
@@ -351,7 +351,7 @@ TEST(PictureLayerTest, ChangingHostsWithCollidingFrames) {
   params2.client = &host_client1;
   params2.settings = &settings;
   params2.task_graph_runner = &task_graph_runner;
-  params2.main_task_runner = base::ThreadTaskRunnerHandle::Get();
+  params2.main_task_runner = base::SingleThreadTaskRunner::GetCurrentDefault();
   params2.client = &host_client2;
   params2.mutator_host = animation_host2.get();
   std::unique_ptr<LayerTreeHost> host2 = LayerTreeHost::CreateSingleThreaded(