Remove the feature SkipCompositingSmallScrollers

We do not need the feature any more since the experiment of not
compositing small scrollers is done. See crbug.com/684631.

Bug: 775643
Cq-Include-Trybots: master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2
Change-Id: I9f0d6c82ffd4d3813630b74ed20f4d44d7fd166f
Reviewed-on: https://chromium-review.googlesource.com/723982Reviewed-by: Jochen Eisinger <jochen@chromium.org>
Commit-Queue: Yi Gu <yigu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#510102}

content/child/runtime_features.cc

@@ -306,9 +306,6 @@ void SetRuntimeFeaturesDefaultsAndUpdateFromArgs(
   if (base::FeatureList::IsEnabled(features::kCompositorTouchAction))
     WebRuntimeFeatures::EnableCompositorTouchAction(true);
 
-  if (base::FeatureList::IsEnabled(features::kSkipCompositingSmallScrollers))
-    WebRuntimeFeatures::EnableSkipCompositingSmallScrollers(true);
-
   if (base::FeatureList::IsEnabled(features::kGenericSensor)) {
     WebRuntimeFeatures::EnableGenericSensor(true);
     if (base::FeatureList::IsEnabled(features::kGenericSensorExtraClasses))

content/public/common/content_features.cc

@@ -288,10 +288,6 @@ const base::Feature kSignInProcessIsolation{"sign-in-process-isolation",
 const base::Feature kSitePerProcess{"site-per-process",
                                     base::FEATURE_DISABLED_BY_DEFAULT};
 
-// An experiment for skipping compositing small scrollers.
-const base::Feature kSkipCompositingSmallScrollers{
-    "SkipCompositingSmallScrollers", base::FEATURE_DISABLED_BY_DEFAULT};
-
 // Paint invalidation based on slimming paint. See https://goo.gl/eQczQW
 const base::Feature kSlimmingPaintInvalidation{
     "SlimmingPaintInvalidation", base::FEATURE_ENABLED_BY_DEFAULT};

content/public/common/content_features.h

@@ -77,7 +77,6 @@ CONTENT_EXPORT extern const base::Feature kServiceWorkerPaymentApps;
 CONTENT_EXPORT extern const base::Feature kServiceWorkerScriptStreaming;
 CONTENT_EXPORT extern const base::Feature kSignInProcessIsolation;
 CONTENT_EXPORT extern const base::Feature kSitePerProcess;
-CONTENT_EXPORT extern const base::Feature kSkipCompositingSmallScrollers;
 CONTENT_EXPORT extern const base::Feature kSlimmingPaintInvalidation;
 CONTENT_EXPORT extern const base::Feature kTimerThrottlingForHiddenFrames;
 CONTENT_EXPORT extern const base::Feature kTopDocumentIsolation;

third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp

@@ -96,11 +96,6 @@ namespace {
 // minimum size used by firefox is 15x15.
 static const int kDefaultMinimumWidthForResizing = 15;
 static const int kDefaultMinimumHeightForResizing = 15;
-// By not compositing scrollers smaller than 160000px (400 * 400), on android
-// devices we might affect roughly 90% scrollers for memory saving while at
-// most 30% scrolls may be slowed down. On non-android devices, it  affects
-// roughly 50% scrollers and 13% scrolls.
-static constexpr int kSmallScrollerThreshold = 160000;
 
 }  // namespace
 
@@ -1986,17 +1981,8 @@ bool PaintLayerScrollableArea::ComputeNeedsCompositedScrolling(
   if (layer->Size().IsEmpty())
     return false;
 
-  // This is for an experiment aiming at memory save by not compositing certain
-  // scrollers. See http://crbug.com/746018, http://crbug.com/684631.
-  // TODO(yigu): Report this main thread scrolling reason once the patch is
-  // landed.
-  CheckedNumeric<int> size = VisibleContentRect().Width();
-  size *= VisibleContentRect().Height();
   if (!layer_has_been_composited &&
-      ((RuntimeEnabledFeatures::SkipCompositingSmallScrollersEnabled() &&
-        size.ValueOrDefault(std::numeric_limits<int>::max()) <
-            kSmallScrollerThreshold) ||
-       !LayerNodeMayNeedCompositedScrolling(layer))) {
+      !LayerNodeMayNeedCompositedScrolling(layer)) {
     return false;
   }
 

third_party/WebKit/Source/core/paint/PaintLayerScrollableAreaTest.cpp

@@ -455,118 +455,6 @@ TEST_F(PaintLayerScrollableAreaTest, OnlyOpaqueLayersPromoted) {
   EXPECT_FALSE(paint_layer->GraphicsLayerBacking());
 }
 
-// Test that small scrollers (area < 160000px) don't get promoted.
-TEST_F(PaintLayerScrollableAreaTest, SmallScrollerPromotionTest) {
-  GetDocument().GetFrame()->GetSettings()->SetPreferCompositingToLCDTextEnabled(
-      true);
-  ScopedSkipCompositingSmallScrollersForTest skip_compositing_small_scrollers(
-      true);
-  SetBodyInnerHTML(
-      "<!DOCTYPE html>"
-      "<style>"
-      " .smallBox { overflow: scroll; width: 100px; height: 100px; }"
-      " .spacer { height: 2000px; }"
-      "</style>"
-      "<div id='small' class='smallBox'><div class='spacer'></div></div>");
-  GetDocument().View()->UpdateAllLifecyclePhases();
-
-  EXPECT_TRUE(RuntimeEnabledFeatures::SkipCompositingSmallScrollersEnabled());
-  Element* small_scroller = GetDocument().getElementById("small");
-  PaintLayer* small_layer =
-      ToLayoutBoxModelObject(small_scroller->GetLayoutObject())->Layer();
-  ASSERT_TRUE(small_layer);
-  EXPECT_FALSE(small_layer->NeedsCompositedScrolling());
-}
-
-// Test that large scrollers get promoted with PreferCompositingToLCDEnabled or
-// other compositing reasons like will-change:transform.
-TEST_F(PaintLayerScrollableAreaTest, LargeScrollerPromotionTest) {
-  GetDocument().GetFrame()->GetSettings()->SetPreferCompositingToLCDTextEnabled(
-      false);
-  ScopedSkipCompositingSmallScrollersForTest skip_compositing_small_scrollers(
-      true);
-  SetBodyInnerHTML(
-      "<!DOCTYPE html>"
-      "<style>"
-      " .largeBox { overflow: scroll; width: 400px; height: 400px; }"
-      " .composited { will-change: transform; }"
-      " .spacer { height: 2000px; }"
-      "</style>"
-      "<div id='largeBox1' class='composited largeBox'>"
-      " <div class='spacer'></div>"
-      "</div>"
-      "<div id='largeBox2' class='largeBox'><div class='spacer'></div></div>");
-  GetDocument().View()->UpdateAllLifecyclePhases();
-
-  EXPECT_TRUE(RuntimeEnabledFeatures::SkipCompositingSmallScrollersEnabled());
-
-  Element* large_scroller = GetDocument().getElementById("largeBox1");
-  PaintLayer* large_layer =
-      ToLayoutBoxModelObject(large_scroller->GetLayoutObject())->Layer();
-  ASSERT_TRUE(large_layer);
-  EXPECT_TRUE(large_layer->NeedsCompositedScrolling());
-
-  large_scroller = GetDocument().getElementById("largeBox2");
-  large_layer =
-      ToLayoutBoxModelObject(large_scroller->GetLayoutObject())->Layer();
-  ASSERT_TRUE(large_layer);
-  EXPECT_FALSE(large_layer->NeedsCompositedScrolling());
-
-  GetDocument().GetFrame()->GetSettings()->SetPreferCompositingToLCDTextEnabled(
-      true);
-  GetDocument().View()->UpdateAllLifecyclePhases();
-  EXPECT_TRUE(large_layer->NeedsCompositedScrolling());
-}
-
-// Test that small scrollers with separate compositing reasons get promoted.
-TEST_F(PaintLayerScrollableAreaTest,
-       SmallScrollerWithSeparateCompositingReasonPromotionTest) {
-  GetDocument().GetFrame()->GetSettings()->SetPreferCompositingToLCDTextEnabled(
-      true);
-  ScopedSkipCompositingSmallScrollersForTest skip_compositing_small_scrollers(
-      true);
-  SetBodyInnerHTML(
-      "<!DOCTYPE html>"
-      "<style>"
-      " .smallBox { overflow: scroll; width: 100px; height: 100px; }"
-      " .composited { backface-visibility: hidden; }"
-      " .composited2 { will-change: transform; }"
-      " .spacer { height: 2000px; }"
-      "</style>"
-      "<div id='box1' class='composited smallBox'>"
-      " <div class='spacer'></div>"
-      "</div>"
-      "<div id='box2' class='composited2 smallBox'>"
-      " <div class='spacer'></div>"
-      "</div>"
-      "<div class='composited smallBox'>"
-      " <div id='box3' style='opacity: 0.5;' class='smallBox'>"
-      "  <div class='spacer'></div>"
-      " </div>"
-      " <div class='spacer'></div>"
-      "</div>");
-  GetDocument().View()->UpdateAllLifecyclePhases();
-
-  EXPECT_TRUE(RuntimeEnabledFeatures::SkipCompositingSmallScrollersEnabled());
-  Element* small_scroller = GetDocument().getElementById("box1");
-  PaintLayer* small_layer =
-      ToLayoutBoxModelObject(small_scroller->GetLayoutObject())->Layer();
-  ASSERT_TRUE(small_layer);
-  EXPECT_TRUE(small_layer->NeedsCompositedScrolling());
-
-  small_scroller = GetDocument().getElementById("box2");
-  small_layer =
-      ToLayoutBoxModelObject(small_scroller->GetLayoutObject())->Layer();
-  ASSERT_TRUE(small_layer);
-  EXPECT_TRUE(small_layer->NeedsCompositedScrolling());
-
-  small_scroller = GetDocument().getElementById("box3");
-  small_layer =
-      ToLayoutBoxModelObject(small_scroller->GetLayoutObject())->Layer();
-  ASSERT_TRUE(small_layer);
-  EXPECT_TRUE(small_layer->NeedsCompositedScrolling());
-}
-
 // Test that <input> elements get promoted with "will-change:transform".
 TEST_F(PaintLayerScrollableAreaTest, InputElementPromotionTest) {
   SetBodyInnerHTML(

third_party/WebKit/Source/platform/exported/WebRuntimeFeatures.cpp

@@ -280,10 +280,6 @@ void WebRuntimeFeatures::EnableScriptedSpeech(bool enable) {
   RuntimeEnabledFeatures::SetScriptedSpeechEnabled(enable);
 }
 
-void WebRuntimeFeatures::EnableSkipCompositingSmallScrollers(bool enable) {
-  RuntimeEnabledFeatures::SetSkipCompositingSmallScrollersEnabled(enable);
-}
-
 void WebRuntimeFeatures::EnableSlimmingPaintV2(bool enable) {
   RuntimeEnabledFeatures::SetSlimmingPaintV2Enabled(enable);
 }

third_party/WebKit/Source/platform/runtime_enabled_features.json5

@@ -952,9 +952,6 @@
       name: "SignatureBasedIntegrity",
       status: "experimental",
     },
-    {
-      name: "SkipCompositingSmallScrollers",
-    },
     {
       name: "SlimmingPaintStrictCullRectClipping",
     },

third_party/WebKit/Source/platform/testing/RuntimeEnabledFeaturesTestHelpers.h

@@ -68,10 +68,6 @@ typedef ScopedRuntimeEnabledFeatureForTest<
     RuntimeEnabledFeatures::OverlayScrollbarsEnabled,
     RuntimeEnabledFeatures::SetOverlayScrollbarsEnabled>
     ScopedOverlayScrollbarsForTest;
-typedef ScopedRuntimeEnabledFeatureForTest<
-    RuntimeEnabledFeatures::SkipCompositingSmallScrollersEnabled,
-    RuntimeEnabledFeatures::SetSkipCompositingSmallScrollersEnabled>
-    ScopedSkipCompositingSmallScrollersForTest;
 typedef ScopedRuntimeEnabledFeatureForTest<
     RuntimeEnabledFeatures::ExperimentalCanvasFeaturesEnabled,
     RuntimeEnabledFeatures::SetExperimentalCanvasFeaturesEnabled>

third_party/WebKit/public/platform/WebRuntimeFeatures.h

@@ -134,7 +134,6 @@ class WebRuntimeFeatures {
   BLINK_PLATFORM_EXPORT static void EnableServiceWorkerNavigationPreload(bool);
   BLINK_PLATFORM_EXPORT static void EnableServiceWorkerScriptStreaming(bool);
   BLINK_PLATFORM_EXPORT static void EnableSharedWorker(bool);
-  BLINK_PLATFORM_EXPORT static void EnableSkipCompositingSmallScrollers(bool);
   BLINK_PLATFORM_EXPORT static void EnableSlimmingPaintV2(bool);
   BLINK_PLATFORM_EXPORT static void EnableTouchEventFeatureDetection(bool);
   BLINK_PLATFORM_EXPORT static void EnableTouchpadAndWheelScrollLatching(bool);