Preloading: Add browser side support of "eager" viewport heuristics

This CL adds a new mojom method, `OnEagerViewportHeuristicTriggered()`
to the `blink.mojom.AnchorElementInteractionHost` interface. The
existing `OnViewportHeuristicTriggered()` method is renamed to
`OnModerateViewportHeuristicTriggered()` to accommodate this change.

No real callers of `OnEagerViewportHeuristicTriggered` are implemented
in this CL. Please refer to crrev.com/c/7059950/ for the usage. All
changes in this CL are gated by the `kPreloadingEagerViewportHeuristics`
feature flag.

Bug: 436705485
Change-Id: Icbacd1216012205442ccabca7f37a04bfab5b0cf
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7058432
Reviewed-by: Takashi Toyoshima <[email protected]>
Reviewed-by: Hiroki Nakagawa <[email protected]>
Commit-Queue: Takashi Nakayama <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1532385}

Author: azaika

content/browser/preloading/anchor_element_interaction_host_impl.cc

@@ -167,13 +167,14 @@ void AnchorElementInteractionHostImpl::OnPointerHoverModerate(
   MaybeWarmUpServiceWorkerOnPointerHover(url, render_frame_host());
 }
 
-void AnchorElementInteractionHostImpl::OnViewportHeuristicTriggered(
+void AnchorElementInteractionHostImpl::OnModerateViewportHeuristicTriggered(
     const GURL& url) {
   if (!base::FeatureList::IsEnabled(
           blink::features::kPreloadingModerateViewportHeuristics)) {
     ReportBadMessageAndDeleteThis(
-        "OnViewportHeuristic should not be called by the renderer without "
-        "blink::features::kPreloadingModerateViewportHeuristics being enabled");
+        "OnModerateViewportHeuristic should not be called by the renderer "
+        "without blink::features::kPreloadingModerateViewportHeuristics being "
+        "enabled");
     return;
   }
 
@@ -182,4 +183,21 @@ void AnchorElementInteractionHostImpl::OnViewportHeuristicTriggered(
   preloading_decider->OnModerateViewportHeuristicTriggered(url);
 }
 
+void AnchorElementInteractionHostImpl::OnEagerViewportHeuristicTriggered(
+    const std::vector<GURL>& target_urls) {
+  if (!base::FeatureList::IsEnabled(
+          blink::features::kPreloadingEagerViewportHeuristics)) {
+    ReportBadMessageAndDeleteThis(
+        "OnEagerViewportHeuristic should not be called by the renderer without "
+        "blink::features::kPreloadingEagerViewportHeuristics being enabled");
+    return;
+  }
+
+  auto* preloading_decider =
+      PreloadingDecider::GetOrCreateForCurrentDocument(&render_frame_host());
+  for (const GURL& url : target_urls) {
+    preloading_decider->OnEagerViewportHeuristicTriggered(url);
+  }
+}
+
 }  // namespace content

content/browser/preloading/anchor_element_interaction_host_impl.h

@@ -36,7 +36,9 @@ class CONTENT_EXPORT AnchorElementInteractionHostImpl
   void OnPointerHoverModerate(
       const GURL& target,
       blink::mojom::AnchorElementPointerDataPtr mouse_data) override;
-  void OnViewportHeuristicTriggered(const GURL& target) override;
+  void OnModerateViewportHeuristicTriggered(const GURL& target) override;
+  void OnEagerViewportHeuristicTriggered(
+      const std::vector<GURL>& targets) override;
 };
 
 }  // namespace content

content/browser/preloading/anchor_element_interaction_host_impl_unittest.cc

@@ -104,7 +104,8 @@ TEST_F(AnchorElementInteractionHostImplTest, OnPointerEvents) {
             blink::mojom::SpeculationEagerness::kEager);
 }
 
-TEST_F(AnchorElementInteractionHostImplTest, OnViewportHeuristicTriggered) {
+TEST_F(AnchorElementInteractionHostImplTest,
+       OnModerateViewportHeuristicTriggered) {
   base::test::ScopedFeatureList feature_list;
   feature_list.InitAndEnableFeature(
       blink::features::kPreloadingModerateViewportHeuristics);
@@ -121,7 +122,7 @@ TEST_F(AnchorElementInteractionHostImplTest, OnViewportHeuristicTriggered) {
                                            remote.BindNewPipeAndPassReceiver());
 
   const GURL url("https://example.com");
-  remote->OnViewportHeuristicTriggered(url);
+  remote->OnModerateViewportHeuristicTriggered(url);
   remote.FlushForTesting();
 
   auto* preloading_data =
@@ -142,10 +143,50 @@ TEST_F(AnchorElementInteractionHostImplTest, OnViewportHeuristicTriggered) {
 }
 
 TEST_F(AnchorElementInteractionHostImplTest,
-       RecallRecordedWhenViewportHeuristicIsNotTriggered) {
+       OnEagerViewportHeuristicTriggered) {
   base::test::ScopedFeatureList feature_list;
   feature_list.InitAndEnableFeature(
-      blink::features::kPreloadingModerateViewportHeuristics);
+      blink::features::kPreloadingEagerViewportHeuristics);
+
+  base::HistogramTester histogram_tester;
+  auto* render_frame_host = static_cast<RenderFrameHostImpl*>(main_rfh());
+
+  std::vector<blink::mojom::SpeculationCandidatePtr> candidates;
+  PreloadingDecider::GetOrCreateForCurrentDocument(render_frame_host)
+      ->UpdateSpeculationCandidates(candidates);
+
+  mojo::Remote<blink::mojom::AnchorElementInteractionHost> remote;
+  AnchorElementInteractionHostImpl::Create(render_frame_host,
+                                           remote.BindNewPipeAndPassReceiver());
+
+  const GURL url("https://example.com");
+  remote->OnEagerViewportHeuristicTriggered({url});
+  remote.FlushForTesting();
+
+  auto* preloading_data =
+      PreloadingDataImpl::GetOrCreateForWebContents(web_contents());
+  EXPECT_EQ(preloading_data->GetPredictionsSizeForTesting(), 1u);
+
+  std::unique_ptr<NavigationSimulator> navigation_simulator =
+      NavigationSimulator::CreateRendererInitiated(url, main_rfh());
+  navigation_simulator->SetTransition(ui::PAGE_TRANSITION_LINK);
+  navigation_simulator->Start();
+
+  histogram_tester.ExpectUniqueSample(
+      "Preloading.Predictor.EagerViewportHeuristic.Precision",
+      PredictorConfusionMatrix::kTruePositive, 1);
+  histogram_tester.ExpectUniqueSample(
+      "Preloading.Predictor.EagerViewportHeuristic.Recall",
+      PredictorConfusionMatrix::kTruePositive, 1);
+}
+
+TEST_F(AnchorElementInteractionHostImplTest,
+       RecallRecordedWhenViewportHeuristicsAreNotTriggered) {
+  base::test::ScopedFeatureList feature_list;
+  feature_list.InitWithFeatures(
+      {blink::features::kPreloadingModerateViewportHeuristics,
+       blink::features::kPreloadingEagerViewportHeuristics},
+      /*disabled_features=*/{});
 
   base::HistogramTester histogram_tester;
 
@@ -162,6 +203,9 @@ TEST_F(AnchorElementInteractionHostImplTest,
   histogram_tester.ExpectUniqueSample(
       "Preloading.Predictor.ViewportHeuristic.Recall",
       PredictorConfusionMatrix::kFalseNegative, 1);
+  histogram_tester.ExpectUniqueSample(
+      "Preloading.Predictor.EagerViewportHeuristic.Recall",
+      PredictorConfusionMatrix::kFalseNegative, 1);
 }
 
 }  // namespace

third_party/blink/public/mojom/preloading/anchor_element_interaction_host.mojom

@@ -37,8 +37,14 @@ interface AnchorElementInteractionHost {
     OnPointerHoverModerate(url.mojom.Url target,
                            AnchorElementPointerData mouse_data);
 
-    // The renderer calls OnViewportHeuristicTriggered for selected anchor
+    // The renderer calls OnModerateViewportHeuristicTriggered for selected
+    // anchor elements that are part of the HTTP family, in the viewport, and
+    // meet certain other criteria used by the heuristic.
+    OnModerateViewportHeuristicTriggered(url.mojom.Url target);
+
+    // The renderer calls OnEagerViewportHeuristicTriggered for selected anchor
     // elements that are part of the HTTP family, in the viewport, and meet
-    // certain other criteria used by the heuristic.
-    OnViewportHeuristicTriggered(url.mojom.Url target);
+    // certain other criteria used by the heuristic. This function accepts
+    // multiple target URLs at once to reduce the number of IPC calls.
+    OnEagerViewportHeuristicTriggered(array<url.mojom.Url> targets);
 };

third_party/blink/renderer/core/loader/anchor_element_interaction_test.cc

@@ -85,9 +85,14 @@ class MockAnchorElementInteractionHost
                       .mouse_velocity = mouse_data->mouse_velocity,
                       .is_eager = false});
   }
-  void OnViewportHeuristicTriggered(const KURL& target) override {
+  void OnModerateViewportHeuristicTriggered(const KURL& target) override {
     calls_.push_back({.url = target, .type = PointerEventType::kNone});
   }
+  void OnEagerViewportHeuristicTriggered(const Vector<KURL>& targets) override {
+    for (const KURL& url : targets) {
+      calls_.push_back({.url = url, .type = PointerEventType::kNone});
+    }
+  }
 
  private:
   mojo::Receiver<mojom::blink::AnchorElementInteractionHost> receiver_{this};

third_party/blink/renderer/core/loader/anchor_element_interaction_tracker.cc

@@ -616,7 +616,7 @@ void AnchorElementInteractionTracker::ViewportHeuristicTimerFired(
     return;
   }
 
-  interaction_host_->OnViewportHeuristicTriggered(
+  interaction_host_->OnModerateViewportHeuristicTriggered(
       largest_anchor_element_in_viewport_->Url());
 }