Update layout instability terminology in core/timing.

This renames Performance::layout_jank_buffer_ and associated objects, as
well as WindowPerformance::AddLayoutJankFraction.

Also remove some references to "jank" in LayoutShiftTracker unit tests.

Bug: 963474
Change-Id: I71877731150008928bf56319bf9631d6326ad0f8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1720997Reviewed-by: Timothy Dresser <tdresser@chromium.org>
Commit-Queue: Steve Kobes <skobes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#681920}

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

@@ -364,8 +364,8 @@ void LayoutShiftTracker::ReportShift(double score_delta,
     WindowPerformance* performance =
         DOMWindowPerformance::performance(*frame.DomWindow());
     if (performance) {
-      performance->AddLayoutJankFraction(score_delta, had_recent_input,
-                                         most_recent_input_timestamp_);
+      performance->AddLayoutShiftValue(score_delta, had_recent_input,
+                                       most_recent_input_timestamp_);
     }
   }
 

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

@@ -158,7 +158,7 @@ TEST_F(LayoutShiftTrackerTest, IgnoreAfterInput) {
 TEST_F(LayoutShiftTrackerTest, CompositedElementMovement) {
   SetBodyInnerHTML(R"HTML(
     <style>
-    #jank {
+    #shift {
       position: relative;
       width: 500px;
       height: 200px;
@@ -176,7 +176,7 @@ TEST_F(LayoutShiftTrackerTest, CompositedElementMovement) {
     </style>
     <div id='container' class='tr'>
       <div id='space'></div>
-      <div id='jank' class='tr'></div>
+      <div id='shift' class='tr'></div>
     </div>
   )HTML");
 
@@ -184,14 +184,14 @@ TEST_F(LayoutShiftTrackerTest, CompositedElementMovement) {
       html_names::kStyleAttr, AtomicString("height: 100px"));
   UpdateAllLifecyclePhases();
 
-  // #jank is 400x200 after viewport intersection with correct application of
-  // composited #container offset, and 100px lower after janking, so jank score
-  // is (400 * 300) * (100 / 800) / (viewport size 800 * 600)
+  // #shift is 400x200 after viewport intersection with correct application of
+  // composited #container offset, and 100px lower after shifting, so shift
+  // score is (400 * 300) * (100 / 800) / (viewport size 800 * 600)
   EXPECT_FLOAT_EQ(0.25 * (100.0 / 800.0), GetLayoutShiftTracker().Score());
 }
 
-TEST_F(LayoutShiftTrackerTest, CompositedJankBeforeFirstPaint) {
-  // Tests that we don't crash if a new layer janks during a second compositing
+TEST_F(LayoutShiftTrackerTest, CompositedShiftBeforeFirstPaint) {
+  // Tests that we don't crash if a new layer shifts during a second compositing
   // update before prepaint sets up property tree state.  See crbug.com/881735
   // (which invokes UpdateLifecycleToCompositingCleanPlusScrolling through
   // accessibilityController.accessibleElementById).
@@ -261,7 +261,7 @@ TEST_F(LayoutShiftTrackerTest, IgnoreSVG) {
   EXPECT_FLOAT_EQ(0, GetLayoutShiftTracker().Score());
 }
 
-TEST_F(LayoutShiftTrackerTest, JankWhileScrolled) {
+TEST_F(LayoutShiftTrackerTest, ShiftWhileScrolled) {
   SetBodyInnerHTML(R"HTML(
     <style>
       body { height: 1000px; margin: 0; }
@@ -367,7 +367,7 @@ TEST_F(LayoutShiftTrackerTest, ShiftInToViewport) {
                                                   AtomicString("top: 400px"));
   UpdateAllLifecyclePhases();
   // The element moves from outside the viewport to within the viewport, which
-  // should generate jank.
+  // should generate a shift.
   // (width 600) * (height 0 + move 200) * (200 / 800) / (800 * 600 viewport)
   EXPECT_FLOAT_EQ(0.25 * (200.0 / 800.0), GetLayoutShiftTracker().Score());
 }
@@ -386,14 +386,14 @@ TEST_F(LayoutShiftTrackerTest, ClipWithoutPaintLayer) {
   )HTML");
 
   // Increase j's top margin by 100px. Since j is clipped by the scroller, this
-  // should not generate jank. However, due to the issue in crbug/971639, this
-  // case was erroneously reported as janking, before that bug was fixed. This
-  // test ensures we do not regress this behavior.
+  // should not generate a shift. However, due to the issue in crbug.com/971639,
+  // this case was erroneously reported as shifting, before that bug was fixed.
+  // This test ensures we do not regress this behavior.
   GetDocument().getElementById("j")->setAttribute(
       html_names::kStyleAttr, AtomicString("margin-top: 100px"));
 
   UpdateAllLifecyclePhases();
-  // Make sure no jank score is reported, since the element that moved is fully
+  // Make sure no shift score is reported, since the element that moved is fully
   // clipped by the scroller.
   EXPECT_FLOAT_EQ(0.0, GetLayoutShiftTracker().Score());
 }

third_party/blink/renderer/core/timing/performance.cc

@@ -97,7 +97,7 @@ using PerformanceObserverVector = HeapVector<Member<PerformanceObserver>>;
 constexpr size_t kDefaultResourceTimingBufferSize = 250;
 constexpr size_t kDefaultEventTimingBufferSize = 150;
 constexpr size_t kDefaultElementTimingBufferSize = 150;
-constexpr size_t kDefaultLayoutJankBufferSize = 150;
+constexpr size_t kDefaultLayoutShiftBufferSize = 150;
 constexpr size_t kDefaultLargestContenfulPaintSize = 150;
 
 Performance::Performance(
@@ -249,8 +249,8 @@ PerformanceEntryVector Performance::getEntriesByTypeInternal(
     case PerformanceEntry::kTaskAttribution:
       break;
     case PerformanceEntry::kLayoutShift:
-      for (const auto& layout_jank : layout_jank_buffer_)
-        entries.push_back(layout_jank);
+      for (const auto& layout_shift : layout_shift_buffer_)
+        entries.push_back(layout_shift);
       break;
     case PerformanceEntry::kLargestContentfulPaint:
       UseCounter::Count(GetExecutionContext(),
@@ -549,9 +549,9 @@ void Performance::AddEventTimingBuffer(PerformanceEventTiming& entry) {
   }
 }
 
-void Performance::AddLayoutJankBuffer(LayoutShift& entry) {
-  if (layout_jank_buffer_.size() < kDefaultLayoutJankBufferSize)
-    layout_jank_buffer_.push_back(&entry);
+void Performance::AddLayoutShiftBuffer(LayoutShift& entry) {
+  if (layout_shift_buffer_.size() < kDefaultLayoutShiftBufferSize)
+    layout_shift_buffer_.push_back(&entry);
 }
 
 void Performance::AddLargestContentfulPaint(LargestContentfulPaint* entry) {
@@ -914,7 +914,7 @@ void Performance::Trace(blink::Visitor* visitor) {
   visitor->Trace(resource_timing_secondary_buffer_);
   visitor->Trace(element_timing_buffer_);
   visitor->Trace(event_timing_buffer_);
-  visitor->Trace(layout_jank_buffer_);
+  visitor->Trace(layout_shift_buffer_);
   visitor->Trace(largest_contentful_paint_buffer_);
   visitor->Trace(navigation_timing_);
   visitor->Trace(user_timing_);

third_party/blink/renderer/core/timing/performance.h

@@ -179,7 +179,7 @@ class CORE_EXPORT Performance : public EventTargetWithInlineData {
   bool IsEventTimingBufferFull() const;
   void AddEventTimingBuffer(PerformanceEventTiming&);
 
-  void AddLayoutJankBuffer(LayoutShift&);
+  void AddLayoutShiftBuffer(LayoutShift&);
 
   void AddLargestContentfulPaint(LargestContentfulPaint*);
 
@@ -350,7 +350,7 @@ class CORE_EXPORT Performance : public EventTargetWithInlineData {
   unsigned event_timing_buffer_max_size_;
   PerformanceEntryVector element_timing_buffer_;
   unsigned element_timing_buffer_max_size_;
-  PerformanceEntryVector layout_jank_buffer_;
+  PerformanceEntryVector layout_shift_buffer_;
   PerformanceEntryVector largest_contentful_paint_buffer_;
   Member<PerformanceEntry> navigation_timing_;
   Member<UserTiming> user_timing_;

third_party/blink/renderer/core/timing/performance_observer_test.cc

@@ -72,9 +72,9 @@ TEST_F(PerformanceObserverTest, ObserveWithBufferedFlag) {
   options->setBuffered(true);
   EXPECT_EQ(0, NumPerformanceEntries());
 
-  // add a layoutjank to performance so getEntries() returns it
+  // add a layout-shift to performance so getEntries() returns it
   auto* entry = MakeGarbageCollected<LayoutShift>(0.0, 1234, true, 5678);
-  base_->AddLayoutJankBuffer(*entry);
+  base_->AddLayoutShiftBuffer(*entry);
 
   // call observe with the buffered flag
   observer_->observe(options, exception_state);

third_party/blink/renderer/core/timing/window_performance.cc

@@ -425,18 +425,18 @@ void WindowPerformance::DispatchFirstInputTiming(
   first_input_timing_ = entry;
 }
 
-void WindowPerformance::AddLayoutJankFraction(double jank_fraction,
-                                              bool input_detected,
-                                              base::TimeTicks input_timestamp) {
+void WindowPerformance::AddLayoutShiftValue(double value,
+                                            bool input_detected,
+                                            base::TimeTicks input_timestamp) {
   DCHECK(RuntimeEnabledFeatures::LayoutInstabilityAPIEnabled(
       GetExecutionContext()));
   auto* entry = MakeGarbageCollected<LayoutShift>(
-      now(), jank_fraction, input_detected,
+      now(), value, input_detected,
       input_detected ? MonotonicTimeToDOMHighResTimeStamp(input_timestamp)
                      : 0.0);
   if (HasObserverFor(PerformanceEntry::kLayoutShift))
     NotifyObserversOfEntry(*entry);
-  AddLayoutJankBuffer(*entry);
+  AddLayoutShiftBuffer(*entry);
 }
 
 void WindowPerformance::OnLargestContentfulPaintUpdated(

third_party/blink/renderer/core/timing/window_performance.h

@@ -84,9 +84,9 @@ class CORE_EXPORT WindowPerformance final : public Performance,
                         const AtomicString& id,
                         Element*);
 
-  void AddLayoutJankFraction(double jank_fraction,
-                             bool input_detected,
-                             base::TimeTicks input_timestamp);
+  void AddLayoutShiftValue(double value,
+                           bool input_detected,
+                           base::TimeTicks input_timestamp);
 
   void OnLargestContentfulPaintUpdated(base::TimeTicks paint_time,
                                        uint64_t paint_size,