Remove JankTrackingSweepLine REF.

Bug: 1000716
Change-Id: Iee211fd0cdb5466fcdaf308a48031f039aaf8258
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1792581Reviewed-by: Jeremy Roman <jbroman@chromium.org>
Commit-Queue: Steve Kobes <skobes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#695043}

third_party/blink/public/platform/web_runtime_features.h

@@ -108,7 +108,6 @@ class WebRuntimeFeatures {
   BLINK_PLATFORM_EXPORT static void EnableGenericSensorExtraClasses(bool);
   BLINK_PLATFORM_EXPORT static void EnableImplicitRootScroller(bool);
   BLINK_PLATFORM_EXPORT static void EnableInputMultipleFieldsUI(bool);
-  BLINK_PLATFORM_EXPORT static void EnableJankTrackingSweepLine(bool);
   BLINK_PLATFORM_EXPORT static void EnableBuiltInModuleAll(bool);
   BLINK_PLATFORM_EXPORT static void EnableBuiltInModuleInfra(bool);
   BLINK_PLATFORM_EXPORT static void EnableBuiltInModuleKvStorage(bool);

third_party/blink/renderer/core/layout/layout_shift_region.h

@@ -12,8 +12,7 @@
 
 namespace blink {
 
-// Represents a per-frame layout shift region for LayoutShiftTracker. Only used
-// when the JankTrackingSweepLine feature is enabled.
+// Represents a per-frame layout shift region for LayoutShiftTracker.
 //
 // This class uses a sweep line algorithm to compute the area in O(n log n) time
 // where n is the number of rects recorded by AddRect. For complex layout shift

third_party/blink/renderer/core/layout/layout_shift_tracker.cc

@@ -28,8 +28,7 @@ namespace blink {
 
 static constexpr base::TimeDelta kTimerDelay =
     base::TimeDelta::FromMilliseconds(500);
-static const float kRegionGranularitySteps = 60.0;
-// TODO: Vary by Finch experiment parameter.
+// TODO(crbug.com/1000716): Remove granularity scaling logic.
 static const float kSweepLineRegionGranularity = 1.0;
 static const float kMovementThreshold = 3.0;  // CSS pixels.
 
@@ -53,11 +52,7 @@ static float GetMoveDistance(const FloatRect& old_rect,
 
 float LayoutShiftTracker::RegionGranularityScale(
     const IntRect& viewport) const {
-  if (RuntimeEnabledFeatures::JankTrackingSweepLineEnabled())
-    return kSweepLineRegionGranularity;
-
-  return kRegionGranularitySteps /
-         std::min(viewport.Height(), viewport.Width());
+  return kSweepLineRegionGranularity;
 }
 
 static bool EqualWithinMovementThreshold(const FloatPoint& a,
@@ -220,13 +215,9 @@ void LayoutShiftTracker::ObjectShifted(
   visible_old_rect.Scale(scale);
   visible_new_rect.Scale(scale);
 
-  if (RuntimeEnabledFeatures::JankTrackingSweepLineEnabled()) {
-    region_experimental_.AddRect(visible_old_rect);
-    region_experimental_.AddRect(visible_new_rect);
-  } else {
-    region_.Unite(Region(visible_old_rect));
-    region_.Unite(Region(visible_new_rect));
-  }
+  // TODO(crbug.com/1000716): Rename region_experimental_.
+  region_experimental_.AddRect(visible_old_rect);
+  region_experimental_.AddRect(visible_new_rect);
 }
 
 void LayoutShiftTracker::NotifyObjectPrePaint(
@@ -269,7 +260,7 @@ double LayoutShiftTracker::SubframeWeightingFactor() const {
 void LayoutShiftTracker::NotifyPrePaintFinished() {
   if (!IsActive())
     return;
-  bool use_sweep_line = RuntimeEnabledFeatures::JankTrackingSweepLineEnabled();
+  bool use_sweep_line = true;
   bool region_is_empty =
       use_sweep_line ? region_experimental_.IsEmpty() : region_.IsEmpty();
   if (region_is_empty)
@@ -459,10 +450,8 @@ std::unique_ptr<TracedValue> LayoutShiftTracker::PerFrameTraceData(
   float granularity_scale = RegionGranularityScale(
       IntRect(IntPoint(),
               frame_view_->GetScrollableArea()->VisibleContentRect().Size()));
-  if (RuntimeEnabledFeatures::JankTrackingSweepLineEnabled())
-    RegionToTracedValue(region_experimental_, granularity_scale, *value);
-  else
-    RegionToTracedValue(region_, granularity_scale, *value);
+
+  RegionToTracedValue(region_experimental_, granularity_scale, *value);
 
   value->SetBoolean("is_main_frame", frame_view_->GetFrame().IsMainFrame());
   value->SetBoolean("had_recent_input", input_detected);

third_party/blink/renderer/core/layout/layout_shift_tracker_test.cc

@@ -60,23 +60,6 @@ TEST_F(LayoutShiftTrackerTest, SimpleBlockMovement) {
   EXPECT_FLOAT_EQ(60.0, GetLayoutShiftTracker().OverallMaxDistance());
 }
 
-TEST_F(LayoutShiftTrackerTest, GranularitySnapping) {
-  if (RuntimeEnabledFeatures::JankTrackingSweepLineEnabled())
-    return;
-
-  SetBodyInnerHTML(R"HTML(
-    <style>
-      #j { position: relative; width: 304px; height: 104px; }
-    </style>
-    <div id='j'></div>
-  )HTML");
-  GetDocument().getElementById("j")->setAttribute(html_names::kStyleAttr,
-                                                  AtomicString("top: 58px"));
-  UpdateAllLifecyclePhases();
-  // Rect locations and sizes should snap to multiples of 600 / 60 = 10.
-  EXPECT_FLOAT_EQ(0.1, GetLayoutShiftTracker().Score());
-}
-
 TEST_F(LayoutShiftTrackerTest, Transform) {
   SetBodyInnerHTML(R"HTML(
     <style>

third_party/blink/renderer/platform/exported/web_runtime_features.cc

@@ -220,10 +220,6 @@ void WebRuntimeFeatures::EnableInputMultipleFieldsUI(bool enable) {
   RuntimeEnabledFeatures::SetInputMultipleFieldsUIEnabled(enable);
 }
 
-void WebRuntimeFeatures::EnableJankTrackingSweepLine(bool enable) {
-  RuntimeEnabledFeatures::SetJankTrackingSweepLineEnabled(enable);
-}
-
 void WebRuntimeFeatures::EnableBuiltInModuleAll(bool enable) {
   RuntimeEnabledFeatures::SetBuiltInModuleAllEnabled(enable);
 }

third_party/blink/renderer/platform/runtime_enabled_features.json5

@@ -833,12 +833,6 @@
       // world. See crbug.com/896041.
       name: "IsolatedWorldCSP"
     },
-    {
-      // Modifies LayoutShiftTracker to use O(n log n) sweep line algorithm for
-      // computing the area of the layout shift region.
-      name: "JankTrackingSweepLine",
-      status: "stable",
-    },
     {
       name: "JSONModules",
     },