Backed out changeset 847bca011f0f (bug 1674776) for causing bug 1682472 on a CLOSED TREE

dom/animation/DocumentTimeline.cpp

@@ -49,8 +49,6 @@ DocumentTimeline::DocumentTimeline(Document* aDocument,
   if (mDocument) {
     mDocument->Timelines().insertBack(this);
   }
-  // Ensure mLastRefreshDriverTime is valid.
-  UpdateLastRefreshDriverTime();
 }
 
 DocumentTimeline::~DocumentTimeline() {
@@ -99,16 +97,11 @@ bool DocumentTimeline::TracksWallclockTime() const {
 }
 
 TimeStamp DocumentTimeline::GetCurrentTimeStamp() const {
-  nsRefreshDriver* refreshDriver = GetRefreshDriver();
-  return refreshDriver ? refreshDriver->MostRecentRefresh()
-                       : mLastRefreshDriverTime;
-}
-
-void DocumentTimeline::UpdateLastRefreshDriverTime() {
   nsRefreshDriver* refreshDriver = GetRefreshDriver();
   TimeStamp refreshTime =
       refreshDriver ? refreshDriver->MostRecentRefresh() : TimeStamp();
 
+  // Always return the same object to benefit from return-value optimization.
   TimeStamp result =
       !refreshTime.IsNull() ? refreshTime : mLastRefreshDriverTime;
 
@@ -132,6 +125,8 @@ void DocumentTimeline::UpdateLastRefreshDriverTime() {
   if (!refreshTime.IsNull()) {
     mLastRefreshDriverTime = refreshTime;
   }
+
+  return result;
 }
 
 Nullable<TimeDuration> DocumentTimeline::ToTimelineTime(

dom/animation/DocumentTimeline.h

@@ -68,8 +68,6 @@ class DocumentTimeline final : public AnimationTimeline,
 
   Document* GetDocument() const override { return mDocument; }
 
-  void UpdateLastRefreshDriverTime();
-
  protected:
   TimeStamp GetCurrentTimeStamp() const;
   nsRefreshDriver* GetRefreshDriver() const;
@@ -83,7 +81,7 @@ class DocumentTimeline final : public AnimationTimeline,
   // The most recently used refresh driver time. This is used in cases where
   // we don't have a refresh driver (e.g. because we are in a display:none
   // iframe).
-  TimeStamp mLastRefreshDriverTime;
+  mutable TimeStamp mLastRefreshDriverTime;
   bool mIsObservingRefreshDriver;
 
   TimeDuration mOriginTime;

dom/animation/EffectCompositor.cpp

@@ -953,12 +953,6 @@ bool EffectCompositor::PreTraverseInSubtree(ServoTraversalFlags aFlags,
     }
   }
 
-  if (foundElementsNeedingRestyle) {
-    // Update the last refresh driver time in the timeline to avoid mutating it
-    // during parallel styling.
-    mPresContext->Document()->Timeline()->UpdateLastRefreshDriverTime();
-  }
-
   return foundElementsNeedingRestyle;
 }
 

mozglue/build/TsanOptions.cpp

@@ -266,6 +266,9 @@ extern "C" const char* __tsan_default_suppressions() {
          "race:VRShMem::PullSystemState\n"
          "race:VRShMem::PushSystemState\n"
 
+         // Bug 1674776
+         "race:DocumentTimeline::GetCurrentTimeAsDuration\n"
+
          // Bug 1674835
          "race:nsHttpTransaction::ReadSegments\n"
          "race:nsHttpTransaction::SecurityInfo\n"