Bug 1354501 - Bail out if we know there is no need to dispatch any animation events in advance of checking which animation event we need. r=birtles

MozReview-Commit-ID: JhOs0CD49R

--HG--
extra : rebase_source : dd4c779ed23eb4f728192fdc27536f4409de2c55

layout/style/nsAnimationManager.cpp

@@ -202,6 +202,9 @@ CSSAnimation::QueueEvents(const StickyTimeDuration& aActiveTime)
   if (!mEffect) {
     currentPhase = GetAnimationPhaseWithoutEffect
       <ComputedTiming::AnimationPhase>(*this);
+    if (currentPhase == mPreviousPhase) {
+      return;
+    }
   } else {
     ComputedTiming computedTiming = mEffect->GetComputedTiming();
     currentPhase = computedTiming.mPhase;

layout/style/nsTransitionManager.cpp

@@ -210,6 +210,16 @@ CSSTransition::QueueEvents(const StickyTimeDuration& aActiveTime)
     intervalEndTime = IntervalEndTime(computedTiming.mActiveDuration);
   }
 
+  if (mPendingState != PendingState::NotPending &&
+      (mPreviousTransitionPhase == TransitionPhase::Idle ||
+       mPreviousTransitionPhase == TransitionPhase::Pending)) {
+    currentPhase = TransitionPhase::Pending;
+  }
+
+  if (currentPhase == mPreviousTransitionPhase) {
+    return;
+  }
+
   // TimeStamps to use for ordering the events when they are dispatched. We
   // use a TimeStamp so we can compare events produced by different elements,
   // perhaps even with different timelines.
@@ -219,13 +229,6 @@ CSSTransition::QueueEvents(const StickyTimeDuration& aActiveTime)
   TimeStamp startTimeStamp = ElapsedTimeToTimeStamp(intervalStartTime);
   TimeStamp endTimeStamp   = ElapsedTimeToTimeStamp(intervalEndTime);
 
-  if (mPendingState != PendingState::NotPending &&
-      (mPreviousTransitionPhase == TransitionPhase::Idle ||
-       mPreviousTransitionPhase == TransitionPhase::Pending))
-  {
-    currentPhase = TransitionPhase::Pending;
-  }
-
   AutoTArray<AnimationEventInfo, 3> events;
 
   auto appendTransitionEvent = [&](EventMessage aMessage,