Add "eager" viewport heuristics support to PreloadingDecider

To accommodate a new "eager" viewport heuristic, the existing
`OnViewportHeuristicTriggered()` method is renamed to
`OnModerateViewportHeuristicTriggered()`.

A new method, `OnEagerViewportHeuristicTriggered()`, is added. This
method is gated by the `kPreloadingEagerViewportHeuristics` feature flag
and calls `MaybeEnactCandidate` with the `kEagerViewportHeuristic`
predictor.

Call sites and unit tests are updated to use the new 'moderate' function
name. New tests are also added to cover the 'eager' heuristic's
behavior.

Bug: 436705485
Change-Id: I4396749b5067a131ad0ab6079ce2336fec48d280
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7058431
Commit-Queue: Takashi Nakayama <[email protected]>
Reviewed-by: Hiroki Nakagawa <[email protected]>
Reviewed-by: Lingqi Chi <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1532384}

Author: azaika

content/browser/preloading/anchor_element_interaction_host_impl.cc

@@ -179,7 +179,7 @@ void AnchorElementInteractionHostImpl::OnViewportHeuristicTriggered(
 
   auto* preloading_decider =
       PreloadingDecider::GetOrCreateForCurrentDocument(&render_frame_host());
-  preloading_decider->OnViewportHeuristicTriggered(url);
+  preloading_decider->OnModerateViewportHeuristicTriggered(url);
 }
 
 }  // namespace content

content/browser/preloading/preloading_decider.cc

@@ -351,7 +351,7 @@ void PreloadingDecider::OnPointerHover(
                       eagerness_to_exclude);
 }
 
-void PreloadingDecider::OnViewportHeuristicTriggered(const GURL& url) {
+void PreloadingDecider::OnModerateViewportHeuristicTriggered(const GURL& url) {
   CHECK(base::FeatureList::IsEnabled(
       blink::features::kPreloadingModerateViewportHeuristics));
   static const base::FeatureParam<bool> kShouldEnactCandidates{
@@ -371,6 +371,15 @@ void PreloadingDecider::OnViewportHeuristicTriggered(const GURL& url) {
                       /*eagerness_to_exclude=*/{});
 }
 
+void PreloadingDecider::OnEagerViewportHeuristicTriggered(const GURL& url) {
+  CHECK(base::FeatureList::IsEnabled(
+      blink::features::kPreloadingEagerViewportHeuristics));
+  MaybeEnactCandidate(url, preloading_predictor::kEagerViewportHeuristic,
+                      PreloadingConfidence{100},
+                      /*fallback_to_preconnect=*/false,
+                      /*eagerness_to_exclude=*/{});
+}
+
 void PreloadingDecider::MaybeEnactCandidate(
     const GURL& url,
     const PreloadingPredictor& enacting_predictor,

content/browser/preloading/preloading_decider.h

@@ -59,8 +59,11 @@ class CONTENT_EXPORT PreloadingDecider
   //  Receives and processes ML model score for 'url' target link.
   void OnPreloadingHeuristicsModelDone(const GURL& url, float score);
 
-  // Receives and processes 'url' selected by viewport heuristic.
-  void OnViewportHeuristicTriggered(const GURL& url);
+  // Receives and processes `url` selected by "moderate" viewport heuristic.
+  void OnModerateViewportHeuristicTriggered(const GURL& url);
+
+  // Receives and processes `url` selected by "eager" viewport heuristic.
+  void OnEagerViewportHeuristicTriggered(const GURL& url);
 
   // Sets the new preloading decider observer for testing and returns the old
   // one.

content/browser/preloading/preloading_decider_unittest.cc

@@ -1033,7 +1033,8 @@ TEST_F(PreloadingDeciderTest,
       /*100*(75-0/500)=*/15, 1);
 }
 
-TEST_F(PreloadingDeciderTest, ViewportHeuristicPredictionIsNotEnacted) {
+TEST_F(PreloadingDeciderTest,
+       ModerateViewportHeuristicPredictionIsNotEnactedIfDisabled) {
   base::test::ScopedFeatureList feature_list;
   feature_list.InitAndEnableFeatureWithParameters(
       blink::features::kPreloadingModerateViewportHeuristics,
@@ -1051,13 +1052,14 @@ TEST_F(PreloadingDeciderTest, ViewportHeuristicPredictionIsNotEnacted) {
   candidates.push_back(std::move(candidate));
   preloading_decider->UpdateSpeculationCandidates(candidates);
 
-  preloading_decider->OnViewportHeuristicTriggered(url);
+  preloading_decider->OnModerateViewportHeuristicTriggered(url);
   const auto& prefetches = GetPrefetchService()->prefetches_;
   EXPECT_TRUE(prefetches.empty());
 }
 
-TEST_F(PreloadingDeciderTest,
-       ViewportHeuristicPredictionIsEnactedForModeratePrefetchCandidate) {
+TEST_F(
+    PreloadingDeciderTest,
+    ModerateViewportHeuristicPredictionIsEnactedForModeratePrefetchCandidate) {
   base::test::ScopedFeatureList feature_list;
   feature_list.InitAndEnableFeatureWithParameters(
       blink::features::kPreloadingModerateViewportHeuristics,
@@ -1076,7 +1078,7 @@ TEST_F(PreloadingDeciderTest,
   candidates.push_back(std::move(candidate));
   preloading_decider->UpdateSpeculationCandidates(candidates);
 
-  preloading_decider->OnViewportHeuristicTriggered(url);
+  preloading_decider->OnModerateViewportHeuristicTriggered(url);
   const auto& prefetches = GetPrefetchService()->prefetches_;
   ASSERT_EQ(prefetches.size(), 1u);
   EXPECT_EQ(prefetches[0]->GetURL(), url);
@@ -1095,7 +1097,44 @@ TEST_F(PreloadingDeciderTest,
 }
 
 TEST_F(PreloadingDeciderTest,
-       ViewportHeuristicIsEnactedForModeratePrerenderCandidate) {
+       EagerViewportHeuristicPredictionIsEnactedForEagerPrefetchCandidate) {
+  base::test::ScopedFeatureList feature_list;
+  feature_list.InitAndEnableFeature(
+      blink::features::kPreloadingEagerViewportHeuristics);
+
+  base::HistogramTester histogram_tester;
+  auto* preloading_decider =
+      PreloadingDecider::GetOrCreateForCurrentDocument(&GetPrimaryMainFrame());
+  ASSERT_TRUE(preloading_decider != nullptr);
+
+  const GURL url("https://example.com");
+  std::vector<blink::mojom::SpeculationCandidatePtr> candidates;
+  auto candidate =
+      MakeCandidate(url, blink::mojom::SpeculationAction::kPrefetch,
+                    blink::mojom::SpeculationEagerness::kEager);
+  candidates.push_back(std::move(candidate));
+  preloading_decider->UpdateSpeculationCandidates(candidates);
+
+  preloading_decider->OnEagerViewportHeuristicTriggered(url);
+  const auto& prefetches = GetPrefetchService()->prefetches_;
+  ASSERT_EQ(prefetches.size(), 1u);
+  EXPECT_EQ(prefetches[0]->GetURL(), url);
+
+  std::unique_ptr<NavigationSimulator> navigation =
+      NavigationSimulator::CreateRendererInitiated(url, main_rfh());
+  navigation->SetTransition(ui::PAGE_TRANSITION_LINK);
+  navigation->Start();
+
+  histogram_tester.ExpectUniqueSample(
+      "Preloading.Predictor.EagerViewportHeuristic.Precision",
+      PredictorConfusionMatrix::kTruePositive, 1);
+  histogram_tester.ExpectUniqueSample(
+      "Preloading.Predictor.EagerViewportHeuristic.Recall",
+      PredictorConfusionMatrix::kTruePositive, 1);
+}
+
+TEST_F(PreloadingDeciderTest,
+       ModerateViewportHeuristicIsEnactedForModeratePrerenderCandidate) {
   base::test::ScopedFeatureList feature_list;
   feature_list.InitAndEnableFeatureWithParameters(
       blink::features::kPreloadingModerateViewportHeuristics,
@@ -1114,17 +1153,43 @@ TEST_F(PreloadingDeciderTest,
   candidates.push_back(std::move(candidate));
   preloading_decider->UpdateSpeculationCandidates(candidates);
 
-  preloading_decider->OnViewportHeuristicTriggered(url);
+  preloading_decider->OnModerateViewportHeuristicTriggered(url);
   ASSERT_EQ(mock_prerender.Get()->prerenders_.size(), 1u);
   EXPECT_EQ(mock_prerender.Get()->prerenders_[0].first, url);
 }
 
 TEST_F(PreloadingDeciderTest,
-       ViewportHeuristicIsNotEnactedForConservativePrefetchCandidate) {
+       EagerViewportHeuristicIsEnactedForEagerPrerenderCandidate) {
   base::test::ScopedFeatureList feature_list;
-  feature_list.InitAndEnableFeatureWithParameters(
-      blink::features::kPreloadingModerateViewportHeuristics,
-      {{"enact_candidates", "true"}});
+  feature_list.InitAndEnableFeature(
+      blink::features::kPreloadingEagerViewportHeuristics);
+
+  auto* preloading_decider =
+      PreloadingDecider::GetOrCreateForCurrentDocument(&GetPrimaryMainFrame());
+  ASSERT_TRUE(preloading_decider != nullptr);
+  ScopedMockPrerenderer mock_prerender(preloading_decider);
+
+  const GURL url("https://example.com");
+  std::vector<blink::mojom::SpeculationCandidatePtr> candidates;
+  auto candidate =
+      MakeCandidate(url, blink::mojom::SpeculationAction::kPrerender,
+                    blink::mojom::SpeculationEagerness::kEager);
+  candidates.push_back(std::move(candidate));
+  preloading_decider->UpdateSpeculationCandidates(candidates);
+
+  preloading_decider->OnEagerViewportHeuristicTriggered(url);
+  ASSERT_EQ(mock_prerender.Get()->prerenders_.size(), 1u);
+  EXPECT_EQ(mock_prerender.Get()->prerenders_[0].first, url);
+}
+
+TEST_F(PreloadingDeciderTest,
+       ViewportHeuristicsAreNotEnactedForConservativePrefetchCandidate) {
+  base::test::ScopedFeatureList feature_list;
+  feature_list.InitWithFeaturesAndParameters(
+      {{blink::features::kPreloadingModerateViewportHeuristics,
+        {{"enact_candidates", "true"}}},
+       {blink::features::kPreloadingEagerViewportHeuristics, {}}},
+      /*disabled_features=*/{});
 
   auto* preloading_decider =
       PreloadingDecider::GetOrCreateForCurrentDocument(&GetPrimaryMainFrame());
@@ -1138,7 +1203,8 @@ TEST_F(PreloadingDeciderTest,
   candidates.push_back(std::move(candidate));
   preloading_decider->UpdateSpeculationCandidates(candidates);
 
-  preloading_decider->OnViewportHeuristicTriggered(url);
+  preloading_decider->OnModerateViewportHeuristicTriggered(url);
+  preloading_decider->OnEagerViewportHeuristicTriggered(url);
   const auto& prefetches = GetPrefetchService()->prefetches_;
   EXPECT_TRUE(prefetches.empty());
 }