Reland "demomode: Delete user created files between shopper sessions"

This is a reland of commit 7166891c62
Fixed MSAN tests.

Original change's description:
> demomode: Delete user created files between shopper sessions
>
> Delete all files under 'MyFiles' and reset demo media data when device
> is idle, which is the end of one shopper session.
>
> Bug: 396731490
> Change-Id: Ic9a2f69f33261661dc771a980f036f14580cf1b0
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6292333
> Reviewed-by: Li Lin <llin@chromium.org>
> Reviewed-by: Hidehiko Abe <hidehiko@chromium.org>
> Commit-Queue: Xiqi Ruan <xiqiruan@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#1433918}

Bug: 396731490
Change-Id: I4ffbb58603780b538a2f0b2e9db1083be623775a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6367236
Reviewed-by: Hidehiko Abe <hidehiko@chromium.org>
Commit-Queue: Xiqi Ruan <xiqiruan@chromium.org>
Reviewed-by: Li Lin <llin@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1437951}

ash/constants/ash_features.cc

@@ -577,6 +577,12 @@ BASE_FEATURE(kDemoModeWallpaperUpdate,
              "DemoModeWallpaperUpdate",
              base::FEATURE_DISABLED_BY_DEFAULT);
 
+// Controls whether clean up local files between shopper session when demo mode
+// sign in is enable. No-op if demo mode sign in is disabled.
+BASE_FEATURE(kDemoModeSignInFileCleanup,
+             "DemoModeSignInFileCleanup",
+             base::FEATURE_DISABLED_BY_DEFAULT);
+
 // Toggle different display features based on user setting and power state
 BASE_FEATURE(kDisplayPerformanceMode,
              "DisplayPerformanceMode",
@@ -3517,6 +3523,10 @@ bool IsDemoModeWallpaperUpdateEnabled() {
   return base::FeatureList::IsEnabled(kDemoModeWallpaperUpdate);
 }
 
+bool IsDemoModeSignInFileCleanupEnabled() {
+  return base::FeatureList::IsEnabled(kDemoModeSignInFileCleanup);
+}
+
 bool IsDeskTemplateSyncEnabled() {
   return base::FeatureList::IsEnabled(kDeskTemplateSync);
 }

ash/constants/ash_features.h

@@ -178,6 +178,8 @@ COMPONENT_EXPORT(ASH_CONSTANTS)
 BASE_DECLARE_FEATURE(kDemoModeSignIn);
 COMPONENT_EXPORT(ASH_CONSTANTS)
 BASE_DECLARE_FEATURE(kDemoModeWallpaperUpdate);
+COMPONENT_EXPORT(ASH_CONSTANTS)
+BASE_DECLARE_FEATURE(kDemoModeSignInFileCleanup);
 COMPONENT_EXPORT(ASH_CONSTANTS) BASE_DECLARE_FEATURE(kDeskTemplateSync);
 COMPONENT_EXPORT(ASH_CONSTANTS)
 BASE_DECLARE_FEATURE(kDeviceActiveClient28DayActiveCheckMembership);
@@ -1093,6 +1095,7 @@ COMPONENT_EXPORT(ASH_CONSTANTS) bool IsDeepLinkingEnabled();
 COMPONENT_EXPORT(ASH_CONSTANTS) bool IsDemoModeAppLandscapeLockedEnabled();
 COMPONENT_EXPORT(ASH_CONSTANTS) bool IsDemoModeSignInEnabled();
 COMPONENT_EXPORT(ASH_CONSTANTS) bool IsDemoModeWallpaperUpdateEnabled();
+COMPONENT_EXPORT(ASH_CONSTANTS) bool IsDemoModeSignInFileCleanupEnabled();
 COMPONENT_EXPORT(ASH_CONSTANTS) bool IsDeskTemplateSyncEnabled();
 COMPONENT_EXPORT(ASH_CONSTANTS) bool IsDisplayPerformanceModeEnabled();
 COMPONENT_EXPORT(ASH_CONSTANTS) bool IsInputDeviceSettingsSplitEnabled();

chrome/browser/ash/login/demo_mode/BUILD.gn

@@ -50,6 +50,7 @@ static_library("demo_mode") {
     "//chrome/browser/ash/policy/core",
     "//chrome/browser/ash/policy/enrollment",
     "//chrome/browser/ash/profiles",
+    "//chrome/browser/chromeos/extensions/login_screen/login/cleanup",
     "//chrome/browser/ui:browser_list",
     "//chrome/common",
     "//chromeos/ash/components/dbus",

chrome/browser/ash/login/demo_mode/DEPS

@@ -29,6 +29,7 @@ include_rules = [
   "+chrome/browser/browser_process_platform_part.h",
   "+chrome/browser/chrome_browser_main_extra_parts.h",
   "+chrome/browser/chrome_browser_main.h",
+  "+chrome/browser/chromeos/extensions/login_screen/login/cleanup",
   "+chrome/browser/component_updater",
   "+chrome/browser/extensions/external_loader.h",
   "+chrome/browser/extensions/external_provider_impl.h",

chrome/browser/ash/login/demo_mode/demo_mode_idle_handler.cc

@@ -4,9 +4,15 @@
 
 #include "chrome/browser/ash/login/demo_mode/demo_mode_idle_handler.h"
 
+#include <optional>
+
+#include "ash/constants/ash_features.h"
 #include "ash/constants/ash_pref_names.h"
 #include "ash/metrics/demo_session_metrics_recorder.h"
 #include "ash/public/cpp/wallpaper/wallpaper_controller.h"
+#include "base/task/sequenced_task_runner.h"
+#include "base/task/task_traits.h"
+#include "base/task/thread_pool.h"
 #include "chrome/browser/profiles/profile_manager.h"
 #include "chromeos/ash/experiences/idle_detector/idle_detector.h"
 #include "components/prefs/pref_service.h"
@@ -52,8 +58,10 @@ void ResetPrefs() {
 
 }  // namespace
 
-DemoModeIdleHandler::DemoModeIdleHandler(DemoModeWindowCloser* window_closer)
-    : window_closer_(window_closer) {
+DemoModeIdleHandler::DemoModeIdleHandler(
+    DemoModeWindowCloser* window_closer,
+    scoped_refptr<base::SequencedTaskRunner> blocking_task_runner)
+    : window_closer_(window_closer), file_cleaner_(blocking_task_runner) {
   user_activity_observer_.Observe(ui::UserActivityDetector::Get());
 }
 
@@ -75,9 +83,26 @@ void DemoModeIdleHandler::OnUserActivity(const ui::Event* event) {
       base::BindRepeating(&DemoModeIdleHandler::OnIdle,
                           weak_ptr_factory_.GetWeakPtr()),
       /*tick_clock=*/nullptr);
-  idle_detector_->Start(kReLuanchDemoAppIdleDuration);
+
+  idle_detector_->Start(
+      idle_time_out_for_test_.value_or(kReLuanchDemoAppIdleDuration));
 }
 
+void DemoModeIdleHandler::AddObserver(Observer* observer) {
+  observers_.AddObserver(observer);
+}
+
+void DemoModeIdleHandler::RemoveObserver(Observer* observer) {
+  observers_.RemoveObserver(observer);
+}
+
+void DemoModeIdleHandler::SetIdleTimeoutForTest(
+    std::optional<base::TimeDelta> timeout) {
+  idle_time_out_for_test_ = std::move(timeout);
+}
+
+// This function is invoked on the task runner of timer. Post task properly on
+// different thread.
 void DemoModeIdleHandler::OnIdle() {
   // Report shopper session dwell time metrics.
   DemoSessionMetricsRecorder::Get()->ReportShopperSessionDwellTime();
@@ -86,6 +111,11 @@ void DemoModeIdleHandler::OnIdle() {
   idle_detector_.reset();
   is_user_active_ = false;
 
+  if (features::IsDemoModeSignInFileCleanupEnabled()) {
+    // The IO tasks will be executed from non-UI thread by  `file_cleaner_`.
+    CleanupLocalFiles();
+  }
+
   window_closer_->StartClosingApps();
   ResetPrefs();
 
@@ -96,4 +126,27 @@ void DemoModeIdleHandler::OnIdle() {
   // TODO(crbug.com/382360715): Restore network if changed by user.
 }
 
+void DemoModeIdleHandler::CleanupLocalFiles() {
+  // TODO(crbug.com/396731796): Maybe only do clean up when there's a change
+  // under "MyFiles". Unmount the mounted archives before the cleanup. Restore
+  // the default download location if user changed it.
+
+  // Note this won't work for emulator since "MyFiles" is not mounted from user
+  // data directory.
+  file_cleaner_.Cleanup(
+      base::BindOnce(&DemoModeIdleHandler::OnLocalFilesCleanupCompleted,
+                     weak_ptr_factory_.GetWeakPtr()));
+}
+
+void DemoModeIdleHandler::OnLocalFilesCleanupCompleted(
+    const std::optional<std::string>& error_message) {
+  if (error_message) {
+    LOG(ERROR) << "Cleanup local files on device idle failed: "
+               << error_message.value();
+    return;
+  }
+
+  observers_.Notify(&Observer::OnLocalFilesCleanupCompleted);
+}
+
 }  // namespace ash

chrome/browser/ash/login/demo_mode/demo_mode_idle_handler.h

@@ -9,8 +9,11 @@
 
 #include "base/functional/callback.h"
 #include "base/memory/weak_ptr.h"
+#include "base/observer_list.h"
+#include "base/observer_list_types.h"
 #include "base/scoped_observation.h"
 #include "chrome/browser/ash/login/demo_mode/demo_mode_window_closer.h"
+#include "chrome/browser/chromeos/extensions/login_screen/login/cleanup/files_cleanup_handler.h"
 #include "ui/base/user_activity/user_activity_detector.h"
 #include "ui/base/user_activity/user_activity_observer.h"
 
@@ -23,7 +26,15 @@ class IdleDetector;
 // and wait for next user.
 class DemoModeIdleHandler : public ui::UserActivityObserver {
  public:
-  explicit DemoModeIdleHandler(DemoModeWindowCloser* window_closer);
+  class Observer : public base::CheckedObserver {
+   public:
+    // Called on local files is cleaned up complete.
+    virtual void OnLocalFilesCleanupCompleted() = 0;
+  };
+
+  DemoModeIdleHandler(
+      DemoModeWindowCloser* window_closer,
+      scoped_refptr<base::SequencedTaskRunner> blocking_task_runner);
   DemoModeIdleHandler(const DemoModeIdleHandler&) = delete;
   DemoModeIdleHandler& operator=(const DemoModeIdleHandler&) = delete;
   ~DemoModeIdleHandler() override;
@@ -31,13 +42,29 @@ class DemoModeIdleHandler : public ui::UserActivityObserver {
   // ui::UserActivityObserver:
   void OnUserActivity(const ui::Event* event) override;
 
+  // Adds an observer to the observer list.
+  void AddObserver(Observer* observer);
+
+  // Removes an observer from the observer list.
+  void RemoveObserver(Observer* observer);
+
+  void SetIdleTimeoutForTest(std::optional<base::TimeDelta> timeout);
+
  private:
+  // Called on idle timeout reaches. Could be invoked on non-UI thread when
+  // using `base::TestMockTimeTaskRunner` for test.
   void OnIdle();
 
+  // Cleans up everything under "MyFiles" and reset "Downloads" folder to
+  // empty.
+  void CleanupLocalFiles();
+  // Populates demo files after cleanup.
+  void OnLocalFilesCleanupCompleted(
+      const std::optional<std::string>& error_message);
+
   // True when the device is not idle.
   bool is_user_active_ = false;
 
-
   // Detect idle when attract loop is not playing. If the attract loop is well
   // function and it is not playing, it indicates that a user is actively engage
   // with device.
@@ -46,9 +73,16 @@ class DemoModeIdleHandler : public ui::UserActivityObserver {
   // Not owned:
   raw_ptr<DemoModeWindowCloser> window_closer_;
 
+  // Cleaner for `MyFiles` directory:
+  chromeos::FilesCleanupHandler file_cleaner_;
+
+  std::optional<base::TimeDelta> idle_time_out_for_test_;
+
   base::ScopedObservation<ui::UserActivityDetector, ui::UserActivityObserver>
       user_activity_observer_{this};
 
+  base::ObserverList<Observer> observers_;
+
   base::WeakPtrFactory<DemoModeIdleHandler> weak_ptr_factory_{this};
 };
 

chrome/browser/ash/login/demo_mode/demo_mode_idle_handler_unittest.cc

@@ -12,6 +12,8 @@
 #include "ash/wallpaper/test_wallpaper_controller_client.h"
 #include "ash/wallpaper/wallpaper_controller_impl.h"
 #include "base/files/scoped_temp_dir.h"
+#include "base/task/sequenced_task_runner.h"
+#include "base/task/thread_pool.h"
 #include "base/test/bind.h"
 #include "base/test/task_environment.h"
 #include "base/time/time.h"
@@ -54,8 +56,9 @@ class DemoModeIdleHandlerTest : public ChromeAshTestBase {
 
     // OK to unretained `this` since the life cycle of `demo_mode_idle_handler_`
     // is the same as the tests.
-    demo_mode_idle_handler_ =
-        std::make_unique<DemoModeIdleHandler>(window_closer_.get());
+    demo_mode_idle_handler_ = std::make_unique<DemoModeIdleHandler>(
+        window_closer_.get(),
+        base::ThreadPool::CreateSequencedTaskRunner({base::MayBlock()}));
   }
   ~DemoModeIdleHandlerTest() override = default;
 

chrome/browser/ash/login/demo_mode/demo_session.cc

@@ -125,8 +125,6 @@ std::vector<std::string> GetIgnorePinPolicyApps() {
 }
 
 // Copies photos into the Downloads directory.
-// TODO(michaelpg): Test this behavior (requires overriding the Downloads
-// directory).
 void InstallDemoMedia(const base::FilePath& offline_resources_path,
                       const base::FilePath& dest_path) {
   if (offline_resources_path.empty()) {
@@ -135,8 +133,10 @@ void InstallDemoMedia(const base::FilePath& offline_resources_path,
   }
 
   base::FilePath src_path = offline_resources_path.Append(kPhotosPath);
-  if (!base::CopyDirectory(src_path, dest_path, false /* recursive */))
+
+  if (!base::CopyDirectory(src_path, dest_path, false /* recursive */)) {
     LOG(ERROR) << "Failed to install demo mode media.";
+  }
 }
 
 std::string GetSwitchOrDefault(std::string_view switch_string,
@@ -536,7 +536,10 @@ void DemoSession::ActiveUserChanged(user_manager::User* active_user) {
 DemoSession::DemoSession()
     : ignore_pin_policy_offline_apps_(GetIgnorePinPolicyApps()),
       remove_splash_screen_fallback_timer_(
-          std::make_unique<base::OneShotTimer>()) {
+          std::make_unique<base::OneShotTimer>()),
+      blocking_task_runner_(base::ThreadPool::CreateSequencedTaskRunner(
+          {base::MayBlock(), base::TaskPriority::USER_BLOCKING,
+           base::TaskShutdownBehavior::SKIP_ON_SHUTDOWN})) {
   // SessionManager may be unset in unit tests.
   if (session_manager::SessionManager::Get()) {
     session_manager_observation_.Observe(
@@ -547,6 +550,9 @@ DemoSession::DemoSession()
 }
 
 DemoSession::~DemoSession() {
+  // Reset observation before destroying `idle_handler_`.
+  idle_handler_observation_.Reset();
+
   user_manager::UserManager::Get()->RemoveSessionStateObserver(this);
 }
 
@@ -579,10 +585,10 @@ void DemoSession::InstallDemoResources() {
   DCHECK(profile);
   const base::FilePath downloads =
       file_manager::util::GetDownloadsFolderForProfile(profile);
-  base::ThreadPool::PostTask(
-      FROM_HERE, {base::TaskPriority::USER_VISIBLE, base::MayBlock()},
-      base::BindOnce(&InstallDemoMedia, components_->resources_component_path(),
-                     downloads));
+  auto install_media = base::BindOnce(
+      &InstallDemoMedia, components_->resources_component_path(), downloads);
+
+  blocking_task_runner_->PostTask(FROM_HERE, std::move(install_media));
 }
 
 void DemoSession::SetKeyboardBrightnessToOneHundredPercentFromCurrentLevel(
@@ -721,6 +727,19 @@ base::FilePath DemoSession::GetDemoAppComponentPath() {
                          components_->default_app_component_path().value()));
 }
 
+DemoModeIdleHandler* DemoSession::GetIdleHandlerForTest() const {
+  return idle_handler_.get();
+}
+
+scoped_refptr<base::SequencedTaskRunner>
+DemoSession::GetBlockingTaskRunnerForTest() {
+  return blocking_task_runner_;
+}
+
+void DemoSession::OnLocalFilesCleanupCompleted() {
+  InstallDemoResources();
+}
+
 void DemoSession::OnDemoAppComponentLoaded() {
   const auto& app_component_version = components_->app_component_version();
   SYSLOG(INFO) << "Demo mode app component version: "
@@ -740,7 +759,9 @@ void DemoSession::OnDemoAppComponentLoaded() {
 
   if (demo_mode::IsDemoAccountSignInEnabled()) {
     CHECK(window_closer_);
-    idle_handler_ = std::make_unique<DemoModeIdleHandler>(window_closer_.get());
+    idle_handler_ = std::make_unique<DemoModeIdleHandler>(
+        window_closer_.get(), blocking_task_runner_);
+    idle_handler_observation_.Observe(idle_handler_.get());
   }
 }
 

chrome/browser/ash/login/demo_mode/demo_session.h

@@ -43,7 +43,8 @@ class DemoComponents;
 // started and the state of demo mode resources.
 class DemoSession : public session_manager::SessionManagerObserver,
                     public user_manager::UserManager::UserSessionStateObserver,
-                    public chromeos::PowerManagerClient::Observer {
+                    public chromeos::PowerManagerClient::Observer,
+                    public DemoModeIdleHandler::Observer {
  public:
   // Type of demo mode configuration.
   // Warning: DemoModeConfig is stored in local state. Existing entries should
@@ -183,10 +184,18 @@ class DemoSession : public session_manager::SessionManagerObserver,
   // if the splash screen is already removed or never shown.
   void RemoveSplashScreen();
 
+  DemoModeIdleHandler* GetIdleHandlerForTest() const;
+
+  // Gets blocking task runner for test to ensure blocking tasks get flushed.
+  scoped_refptr<base::SequencedTaskRunner> GetBlockingTaskRunnerForTest();
+
  private:
   DemoSession();
   ~DemoSession() override;
 
+  // DemoModeIdleHandler::Observer:
+  void OnLocalFilesCleanupCompleted() override;
+
   void OnDemoAppComponentLoaded();
 
   // Get country code and full name in current language pair sorted by their
@@ -195,7 +204,7 @@ class DemoSession : public session_manager::SessionManagerObserver,
   GetSortedCountryCodeAndNamePairList();
 
   // Installs resources for Demo Mode from the offline demo mode resources, such
-  // as apps and media.
+  // as photos and other media.
   void InstallDemoResources();
 
   // Find image path then show the splash screen.
@@ -229,6 +238,9 @@ class DemoSession : public session_manager::SessionManagerObserver,
                           session_manager::SessionManagerObserver>
       session_manager_observation_{this};
 
+  base::ScopedObservation<DemoModeIdleHandler, DemoModeIdleHandler::Observer>
+      idle_handler_observation_{this};
+
   // The fallback timer that ensures the splash screen is removed in case the
   // screensaver app takes an extra long time to be shown.
   std::unique_ptr<base::OneShotTimer> remove_splash_screen_fallback_timer_;
@@ -245,6 +257,10 @@ class DemoSession : public session_manager::SessionManagerObserver,
   // sessions. Constructed while demo app is available.
   std::unique_ptr<DemoModeIdleHandler> idle_handler_;
 
+  // Task runner for file cleanup and re-install demo mode resource at the end
+  // of shopper sessions.
+  scoped_refptr<base::SequencedTaskRunner> blocking_task_runner_;
+
   base::WeakPtrFactory<DemoSession> weak_ptr_factory_{this};
 };
 

chrome/browser/ash/login/demo_mode/demo_session_browsertest.cc

@@ -10,6 +10,11 @@
 #include "ash/constants/ash_pref_names.h"
 #include "base/files/file_path.h"
 #include "base/files/file_util.h"
+#include "base/scoped_observation.h"
+#include "base/test/bind.h"
+#include "base/test/run_until.h"
+#include "chrome/browser/ash/file_manager/path_util.h"
+#include "chrome/browser/ash/login/demo_mode/demo_components.h"
 #include "chrome/browser/ash/login/demo_mode/demo_setup_controller.h"
 #include "chrome/browser/ash/login/login_manager_test.h"
 #include "chrome/browser/ash/login/test/device_state_mixin.h"
@@ -28,6 +33,7 @@
 #include "chrome/browser/ui/browser_list_observer.h"
 #include "chrome/test/base/browser_process_platform_part_test_api_chromeos.h"
 #include "chrome/test/base/ui_test_utils.h"
+#include "chromeos/ash/components/demo_mode/utils/demo_session_utils.h"
 #include "chromeos/constants/chromeos_features.h"
 #include "chromeos/dbus/power/fake_power_manager_client.h"
 #include "components/component_updater/ash/fake_component_manager_ash.h"
@@ -37,6 +43,7 @@
 #include "components/variations/active_field_trials.h"
 #include "content/public/browser/navigation_entry.h"
 #include "content/public/test/browser_test.h"
+#include "content/public/test/test_utils.h"
 #include "net/base/url_util.h"
 
 namespace ash {
@@ -48,7 +55,12 @@ inline constexpr char kDemoModeAppUrl[] =
     "chrome-untrusted://demo-mode-app/index.html";
 
 inline constexpr char kGrowthCampaignsComponentName[] = "growth-campaigns";
+inline constexpr char kDemoResourceComponentName[] = "demo-mode-resources";
 inline constexpr char kCampaignsFileName[] = "campaigns.json";
+inline constexpr char kDemoMediaDirName[] = "media/photos";
+inline constexpr char kDemoPhotoName[] = "photo.jpg";
+
+// inline constexpr base::TimeDelta kDemoIdleTimeout = base::Seconds(90);
 
 void SetDemoConfigPref(DemoSession::DemoModeConfig demo_config) {
   PrefService* prefs = g_browser_process->local_state();
@@ -69,6 +81,8 @@ void CheckNoDemoMode() {
   EXPECT_EQ(DemoSession::DemoModeConfig::kNone, DemoSession::GetDemoConfig());
 }
 
+}  // namespace
+
 // Tests locking device to policy::DEVICE_MODE_DEMO mode. It is an equivalent to
 // going through online demo mode setup or using offline setup.
 class DemoSessionDemoDeviceModeTest : public OobeBaseTest {
@@ -226,17 +240,29 @@ class DemoLoginTestMainExtraParts : public ChromeBrowserMainExtraParts {
         .AppendASCII(kGrowthCampaignsComponentName);
   }
 
+  base::FilePath GetDemoResourceComponentPath() {
+    return components_temp_dir_.GetPath()
+        .AppendASCII("cros-components")
+        .AppendASCII(kDemoResourceComponentName);
+  }
+
   void PostEarlyInitialization() override {
     auto component_manager_ash =
         base::MakeRefCounted<component_updater::FakeComponentManagerAsh>();
     component_manager_ash->set_supported_components(
-        {"demo-mode-app", kGrowthCampaignsComponentName});
+        {"demo-mode-app", kGrowthCampaignsComponentName,
+         kDemoResourceComponentName});
     component_manager_ash->ResetComponentState(
         "demo-mode-app",
         component_updater::FakeComponentManagerAsh::ComponentInfo(
             component_updater::ComponentManagerAsh::Error::NONE,
             base::FilePath("/dev/null"),
             base::FilePath("/run/imageloader/demo-mode-app")));
+    component_manager_ash->ResetComponentState(
+        "demo-mode-resources",
+        component_updater::FakeComponentManagerAsh::ComponentInfo(
+            component_updater::ComponentManagerAsh::Error::NONE,
+            base::FilePath("/dev/null"), GetDemoResourceComponentPath()));
     component_manager_ash->ResetComponentState(
         "growth-campaigns",
         component_updater::FakeComponentManagerAsh::ComponentInfo(
@@ -281,6 +307,7 @@ class DemoSessionLoginTest : public LoginManagerTest,
       content::BrowserMainParts* browser_main_parts) override {
     auto extra_parts = std::make_unique<DemoLoginTestMainExtraParts>();
     growth_campaigns_mounted_path_ = extra_parts->GetGrowthCampaignsPath();
+    demo_resource_mounted_path_ = extra_parts->GetDemoResourceComponentPath();
     static_cast<ChromeBrowserMainParts*>(browser_main_parts)
         ->AddParts(std::move(extra_parts));
     LoginManagerTest::CreatedBrowserMainParts(browser_main_parts);
@@ -351,6 +378,10 @@ class DemoSessionLoginTest : public LoginManagerTest,
     return growth_campaigns_mounted_path_;
   }
 
+  base::FilePath& demo_resource_mounted_path() {
+    return demo_resource_mounted_path_;
+  }
+
   LoginManagerMixin login_manager_mixin_{&mixin_host_};
   DeviceStateMixin device_state_mixin_{
       &mixin_host_, DeviceStateMixin::State::OOBE_COMPLETED_DEMO_MODE};
@@ -358,6 +389,7 @@ class DemoSessionLoginTest : public LoginManagerTest,
   base::OnceClosure on_browser_added_callback_;
   static constexpr double kInitialBrightness = 20.0;
   base::FilePath growth_campaigns_mounted_path_;
+  base::FilePath demo_resource_mounted_path_;
   base::WeakPtrFactory<DemoSessionLoginTest> weak_ptr_factory_{this};
 };
 
@@ -586,5 +618,93 @@ IN_PROC_BROWSER_TEST_F(DemoSessionLoginWithGrowthCampaignTest,
       variations::IsInSyntheticTrialGroup("CrOSGrowthStudy", "CampaignId3"));
 }
 
-}  // namespace
+class DemoSessionLoginIdleHandlerTest : public DemoSessionLoginTest {
+ public:
+  DemoSessionLoginIdleHandlerTest() {
+    scoped_feature_list_.InitWithFeatures(
+        {features::kDemoModeSignInFileCleanup}, {});
+  }
+
+  void SetUpOnMainThread() override {
+    demo_mode::SetForceEnableDemoAccountSignIn(true);
+    DemoSessionLoginTest::SetUpOnMainThread();
+    CreateTestMediaFile();
+  }
+
+  void CreateTestMediaFile() {
+    const base::FilePath media_dir =
+        demo_resource_mounted_path_.AppendASCII(kDemoMediaDirName);
+    CHECK(base::CreateDirectory(media_dir));
+
+    const base::FilePath photo(media_dir.Append(kDemoPhotoName));
+    CHECK(base::WriteFile(photo, "random text"));
+  }
+
+  void FlushIOTasks() {
+    base::RunLoop run_loop;
+    DemoSession::Get()->GetBlockingTaskRunnerForTest()->PostTask(
+        FROM_HERE, run_loop.QuitClosure());
+    run_loop.Run();
+  }
+
+ private:
+  base::test::ScopedFeatureList scoped_feature_list_;
+};
+
+IN_PROC_BROWSER_TEST_F(DemoSessionLoginIdleHandlerTest, CleanUpLocalFiles) {
+  //  Setup initial demo mode resources and start a user session:
+  OpenBrowserAndInstallSystemAppForActiveProfile();
+
+  // Ensure media of resource components gets installed.
+  FlushIOTasks();
+
+  //  Verify the photo was copied to download folder.
+  auto* profile = ProfileManager::GetActiveUserProfile();
+  base::FilePath downloads_path =
+      file_manager::util::GetDownloadsFolderForProfile(profile);
+  base::FilePath photo_file = downloads_path.AppendASCII(kDemoPhotoName);
+  {
+    base::ScopedAllowBlockingForTesting allow_blocking;
+    EXPECT_TRUE(base::PathExists(photo_file));
+  }
+
+  // Shorten the timeout for testing.
+  base::TimeDelta idle_timeout = base::Seconds(2);
+  DemoSession::Get()->GetIdleHandlerForTest()->SetIdleTimeoutForTest(
+      idle_timeout);
+
+  // Mock user activity:
+  ui::UserActivityDetector::Get()->HandleExternalUserActivity();
+  base::FilePath user_created_dir_path;
+  {
+    base::ScopedAllowBlockingForTesting allow_blocking;
+    // Mock user creates a new folder under "MyFiles" and deletes the photo
+    // files.
+    base::ScopedTempDir user_created_dir;
+    base::FilePath my_files_path = profile->GetPath().AppendASCII("MyFiles");
+    EXPECT_TRUE(user_created_dir.CreateUniqueTempDirUnderPath(my_files_path));
+    EXPECT_TRUE(base::DirectoryExists(user_created_dir.GetPath()));
+    EXPECT_TRUE(base::DeleteFile(photo_file));
+    user_created_dir_path = user_created_dir.GetPath();
+  }
+
+  // Wait idle timeout + 1s buffer for invoking the file clean up task.
+  base::RunLoop run_loop{base::RunLoop::Type::kNestableTasksAllowed};
+  base::SingleThreadTaskRunner::GetCurrentDefault()->PostDelayedTask(
+      FROM_HERE, run_loop.QuitClosure(), idle_timeout + base::Seconds(1));
+  run_loop.Run();
+
+  // Wait file clean up tasks to be finished.
+  FlushIOTasks();
+  {
+    base::ScopedAllowBlockingForTesting allow_blocking;
+    // Verify `user_created_dir` was deleted and photo was reset.
+    EXPECT_TRUE(base::test::RunUntil([&user_created_dir_path]() {
+      return !base::DirectoryExists(user_created_dir_path);
+    }));
+    EXPECT_TRUE(base::test::RunUntil(
+        [&photo_file]() { return base::PathExists(photo_file); }));
+  }
+}
+
 }  // namespace ash

chrome/browser/chromeos/extensions/login_screen/login/cleanup/files_cleanup_handler.cc

@@ -65,11 +65,14 @@ bool EnsureDirectoryIsEmpty(const base::FilePath& directory_path,
 
 }  // namespace
 
-FilesCleanupHandler::FilesCleanupHandler() {
-  task_runner_ = base::ThreadPool::CreateTaskRunner(
-      {base::MayBlock(), base::TaskPriority::USER_BLOCKING,
-       base::TaskShutdownBehavior::SKIP_ON_SHUTDOWN});
-}
+FilesCleanupHandler::FilesCleanupHandler()
+    : FilesCleanupHandler(base::ThreadPool::CreateTaskRunner(
+          {base::MayBlock(), base::TaskPriority::USER_BLOCKING,
+           base::TaskShutdownBehavior::SKIP_ON_SHUTDOWN})) {}
+
+FilesCleanupHandler::FilesCleanupHandler(
+    scoped_refptr<base::TaskRunner> task_runner)
+    : task_runner_(task_runner) {}
 
 FilesCleanupHandler::~FilesCleanupHandler() = default;
 

chrome/browser/chromeos/extensions/login_screen/login/cleanup/files_cleanup_handler.h

@@ -19,6 +19,7 @@ namespace chromeos {
 class FilesCleanupHandler : public CleanupHandler {
  public:
   FilesCleanupHandler();
+  explicit FilesCleanupHandler(scoped_refptr<base::TaskRunner> task_runner);
   ~FilesCleanupHandler() override;
 
   // CleanupHandler:
@@ -34,4 +35,4 @@ class FilesCleanupHandler : public CleanupHandler {
 
 }  // namespace chromeos
 
-#endif  //  CHROME_BROWSER_CHROMEOS_EXTENSIONS_LOGIN_SCREEN_LOGIN_CLEANUP_FILES_CLEANUP_HANDLER_H_
+#endif  // CHROME_BROWSER_CHROMEOS_EXTENSIONS_LOGIN_SCREEN_LOGIN_CLEANUP_FILES_CLEANUP_HANDLER_H_