[LCPP] Read-path test: ElementLocator matching <img>s priority bumed to VeryHigh

This CL adds a test case for the read path added in https://crrev.com/c/4672510

The test html is
third_party/blink/web_tests/http/tests/lcp_critical_path_predictor/prioritize_lcp_image.php
, but it requires the following test infra changes to run:
- NonAssociatedWebTestControlHost mojom binding so it can be accessed
  from mojo JS binding. Context: discussion at
  https://chromium.slack.com/archives/CGGGVPSQ4/p1688601297545099
- WebTestContentBrowserClient injects LCPP hint at
  `DidStartNavigation` if it was supplied via
  NonAssociatedWebTestControlHost.
- BUILD.gn files are modified so that they will generate
  wire format protos used for testing from text protos.
- `lcpp` VirtualTestSuite is added, since the test require the
  LCPCriticalPathPredictor feature flag to be enabled until the
  feature is unflagged.

Bug: 1419756
Change-Id: Ib7447341808d2df4e5ca374c42362e872c11b1f0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4673124
Auto-Submit: Kouhei Ueno <kouhei@chromium.org>
Reviewed-by: Takashi Toyoshima <toyoshim@chromium.org>
Reviewed-by: Rakina Zata Amni <rakina@chromium.org>
Commit-Queue: Takashi Toyoshima <toyoshim@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1174559}

content/web_test/browser/web_test_content_browser_client.cc

@@ -366,6 +366,12 @@ void WebTestContentBrowserClient::ExposeInterfacesToRenderer(
       base::BindRepeating(&WebTestContentBrowserClient::BindWebTestControlHost,
                           base::Unretained(this),
                           render_process_host->GetID()));
+
+  registry->AddInterface(
+      base::BindRepeating(
+          &WebTestContentBrowserClient::BindNonAssociatedWebTestControlHost,
+          base::Unretained(this)),
+      ui_task_runner);
 }
 
 void WebTestContentBrowserClient::BindPermissionAutomation(
@@ -657,6 +663,14 @@ void WebTestContentBrowserClient::BindWebTestControlHost(
         render_process_id, std::move(receiver));
 }
 
+void WebTestContentBrowserClient::BindNonAssociatedWebTestControlHost(
+    mojo::PendingReceiver<mojom::NonAssociatedWebTestControlHost> receiver) {
+  if (WebTestControlHost::Get()) {
+    WebTestControlHost::Get()->BindNonAssociatedWebTestControlHost(
+        std::move(receiver));
+  }
+}
+
 #if BUILDFLAG(IS_WIN)
 bool WebTestContentBrowserClient::PreSpawnChild(
     sandbox::TargetConfig* config,

content/web_test/browser/web_test_content_browser_client.h

@@ -160,6 +160,9 @@ class WebTestContentBrowserClient : public ShellContentBrowserClient {
       int render_process_id,
       mojo::PendingAssociatedReceiver<mojom::WebTestControlHost> receiver);
 
+  void BindNonAssociatedWebTestControlHost(
+      mojo::PendingReceiver<mojom::NonAssociatedWebTestControlHost> receiver);
+
   bool block_popups_ = true;
   bool screen_orientation_changed_ = false;
 

content/web_test/browser/web_test_control_host.cc

@@ -685,6 +685,7 @@ bool WebTestControlHost::ResetBrowserAfterWebTest() {
   expected_pixel_hash_.clear();
   test_url_ = GURL();
   prefs_ = blink::web_pref::WebPreferences();
+  lcpp_hint_ = absl::nullopt;
   should_override_prefs_ = false;
   WebTestContentBrowserClient::Get()->SetPopupBlockingEnabled(true);
   WebTestContentBrowserClient::Get()->ResetMockClipboardHosts();
@@ -1065,6 +1066,13 @@ void WebTestControlHost::RenderViewDeleted(RenderViewHost* render_view_host) {
   main_window_render_view_hosts_.erase(render_view_host);
 }
 
+void WebTestControlHost::DidStartNavigation(
+    NavigationHandle* navigation_handle) {
+  if (lcpp_hint_) {
+    navigation_handle->SetLCPPNavigationHint(lcpp_hint_.value());
+  }
+}
+
 void WebTestControlHost::ReadyToCommitNavigation(
     NavigationHandle* navigation_handle) {
   NavigationRequest* request = NavigationRequest::From(navigation_handle);
@@ -1783,6 +1791,11 @@ void WebTestControlHost::DisableAutoResize(const gfx::Size& new_size) {
   main_window_->ResizeWebContentForTests(new_size);
 }
 
+void WebTestControlHost::SetLCPPNavigationHint(
+    blink::mojom::LCPCriticalPathPredictorNavigationTimeHintPtr hint) {
+  lcpp_hint_ = *hint.get();
+}
+
 void WebTestControlHost::GoToOffset(int offset) {
   main_window_->GoBackOrForward(offset);
 }
@@ -1844,6 +1857,10 @@ void WebTestControlHost::PrepareRendererForNextWebTest() {
   //
   // Note: this navigation might happen in a new process, depending on the
   // COOP policy of the previous document.
+
+  // Avoid sending LCPP hint on the about:blank navigation.
+  lcpp_hint_ = absl::nullopt;
+
   NavigationController::LoadURLParams params((GURL(kAboutBlankResetWebTest)));
   params.transition_type = ui::PageTransitionFromInt(ui::PAGE_TRANSITION_TYPED);
   params.should_clear_history_list = true;
@@ -2001,6 +2018,11 @@ void WebTestControlHost::BindWebTestControlHostForRenderer(
   receiver_bindings_.Add(this, std::move(receiver), render_process_id);
 }
 
+void WebTestControlHost::BindNonAssociatedWebTestControlHost(
+    mojo::PendingReceiver<mojom::NonAssociatedWebTestControlHost> receiver) {
+  non_associated_receiver_bindings_.Add(this, std::move(receiver));
+}
+
 mojo::AssociatedRemote<mojom::WebTestRenderFrame>&
 WebTestControlHost::GetWebTestRenderFrameRemote(RenderFrameHost* frame) {
   GlobalRenderFrameHostId key(frame->GetProcess()->GetID(),

content/web_test/browser/web_test_control_host.h

@@ -38,6 +38,7 @@
 #include "mojo/public/cpp/bindings/associated_receiver_set.h"
 #include "mojo/public/cpp/bindings/associated_remote.h"
 #include "third_party/blink/public/common/web_preferences/web_preferences.h"
+#include "third_party/blink/public/mojom/lcp_critical_path_predictor/lcp_critical_path_predictor.mojom.h"
 #include "ui/gfx/geometry/size.h"
 
 class SkBitmap;
@@ -114,7 +115,8 @@ class WebTestResultPrinter {
 class WebTestControlHost : public WebContentsObserver,
                            public RenderProcessHostObserver,
                            public GpuDataManagerObserver,
-                           public mojom::WebTestControlHost {
+                           public mojom::WebTestControlHost,
+                           public mojom::NonAssociatedWebTestControlHost {
  public:
   static WebTestControlHost* Get();
 
@@ -153,6 +155,9 @@ class WebTestControlHost : public WebContentsObserver,
       int render_process_id,
       mojo::PendingAssociatedReceiver<mojom::WebTestControlHost> receiver);
 
+  void BindNonAssociatedWebTestControlHost(
+      mojo::PendingReceiver<mojom::NonAssociatedWebTestControlHost> receiver);
+
   const WebTestRuntimeFlags& web_test_runtime_flags() const {
     return web_test_runtime_flags_;
   }
@@ -190,6 +195,7 @@ class WebTestControlHost : public WebContentsObserver,
   void RenderFrameHostChanged(RenderFrameHost* old_host,
                               RenderFrameHost* new_host) override;
   void RenderViewDeleted(RenderViewHost* render_view_host) override;
+  void DidStartNavigation(NavigationHandle* navigation_handle) override;
   void ReadyToCommitNavigation(NavigationHandle* navigation_handle) override;
   void DidFinishNavigation(NavigationHandle* navigation) override;
 
@@ -261,6 +267,9 @@ class WebTestControlHost : public WebContentsObserver,
   void EnableAutoResize(const gfx::Size& min_size,
                         const gfx::Size& max_size) override;
   void DisableAutoResize(const gfx::Size& new_size) override;
+  void SetLCPPNavigationHint(
+      blink::mojom::LCPCriticalPathPredictorNavigationTimeHintPtr hint)
+      override;
 
   void DiscardMainWindow();
   // Closes all windows opened by the test. This is every window but the main
@@ -358,6 +367,14 @@ class WebTestControlHost : public WebContentsObserver,
   bool should_override_prefs_ = false;
   blink::web_pref::WebPreferences prefs_;
 
+  // When populated, simulate a LCPP backend by sending this hint data along
+  // navigations (typically reload of the same page).
+  // This is set by the LCPP web_tests via
+  // NonAssociatedWebTestControlHost::SetLCPPNavigationHint mojom interface.
+  // This is reset before switching to the next test page.
+  absl::optional<blink::mojom::LCPCriticalPathPredictorNavigationTimeHint>
+      lcpp_hint_;
+
   bool crash_when_leak_found_ = false;
   std::unique_ptr<LeakDetector> leak_detector_;
 
@@ -426,6 +443,9 @@ class WebTestControlHost : public WebContentsObserver,
                               int /*render_process_id*/>
       receiver_bindings_;
 
+  mojo::ReceiverSet<mojom::NonAssociatedWebTestControlHost>
+      non_associated_receiver_bindings_;
+
   base::ScopedTempDir writable_directory_for_tests_;
 
   enum class NextPointerLockAction {

content/web_test/common/web_test.mojom

@@ -8,6 +8,7 @@ import "mojo/public/mojom/base/file_path.mojom";
 import "mojo/public/mojom/base/string16.mojom";
 import "mojo/public/mojom/base/values.mojom";
 import "skia/public/mojom/bitmap.mojom";
+import "third_party/blink/public/mojom/lcp_critical_path_predictor/lcp_critical_path_predictor.mojom"; // presubmit: ignore-long-line
 import "third_party/blink/public/mojom/permissions/permission_status.mojom";
 import "third_party/blink/public/mojom/webpreferences/web_preferences.mojom";
 import "ui/gfx/geometry/mojom/geometry.mojom";
@@ -338,3 +339,15 @@ interface WebTestControlHost {
   // Disable Auto Resize mode, resizing the contents to `new_size`.
   DisableAutoResize(gfx.mojom.Size new_size);
 };
+
+// Web test messages sent from the renderer process to the browser.
+// This provides a message pipe from each renderer to the global
+// WebTestControlHost in the browser.
+// This is very similar to WebTestControlHost, but the interface is not
+// associated to the legacy IPC channel, so can be used from mojo JS binding
+// directly.
+interface NonAssociatedWebTestControlHost {
+  // Provide the specified LCPP navigation time hint to next navigation.
+  SetLCPPNavigationHint(
+      blink.mojom.LCPCriticalPathPredictorNavigationTimeHint hint);
+};