Bug 1674776 - Update DocumentTimeline::mLastRefreshDriverTime outside parallel styling. r=boris,decoder

Note that we can probably use mLastRefreshDriverTime directly in
DocumentTimeline::GetCurrentTimeStamp(), i.e. we don't need to use the refresh
driver there, but I'd preserve the current behavior.

Differential Revision: https://phabricator.services.mozilla.com/D97823

dom/animation/DocumentTimeline.cpp

@@ -49,6 +49,8 @@ DocumentTimeline::DocumentTimeline(Document* aDocument,
   if (mDocument) {
     mDocument->Timelines().insertBack(this);
   }
+  // Ensure mLastRefreshDriverTime is valid.
+  UpdateLastRefreshDriverTime();
 }
 
 DocumentTimeline::~DocumentTimeline() {
@@ -97,11 +99,16 @@ 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;
 
@@ -125,8 +132,6 @@ TimeStamp DocumentTimeline::GetCurrentTimeStamp() const {
   if (!refreshTime.IsNull()) {
     mLastRefreshDriverTime = refreshTime;
   }
-
-  return result;
 }
 
 Nullable<TimeDuration> DocumentTimeline::ToTimelineTime(

dom/animation/DocumentTimeline.h

@@ -68,6 +68,8 @@ class DocumentTimeline final : public AnimationTimeline,
 
   Document* GetDocument() const override { return mDocument; }
 
+  void UpdateLastRefreshDriverTime();
+
  protected:
   TimeStamp GetCurrentTimeStamp() const;
   nsRefreshDriver* GetRefreshDriver() const;
@@ -81,7 +83,7 @@ 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).
-  mutable TimeStamp mLastRefreshDriverTime;
+  TimeStamp mLastRefreshDriverTime;
   bool mIsObservingRefreshDriver;
 
   TimeDuration mOriginTime;

dom/animation/EffectCompositor.cpp

@@ -953,6 +953,12 @@ 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

@@ -266,9 +266,6 @@ 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"