Web Animations: Avoid iteration when checking for outdated animations on timeline

Source/core/animation/AnimationTimeline.cpp

Index: Source/core/animation/AnimationTimeline.cpp
diff --git a/Source/core/animation/AnimationTimeline.cpp b/Source/core/animation/AnimationTimeline.cpp
index 82af9a72ebc204cedf0ef3100ce996c89446b864..7827a075bfe9dffa5435b517aa07110ae10f5cc1 100644
--- a/Source/core/animation/AnimationTimeline.cpp
+++ b/Source/core/animation/AnimationTimeline.cpp
@@ -68,6 +68,7 @@ AnimationTimeline::AnimationTimeline(Document* document, PassOwnPtrWillBeRawPtr<
     : m_document(document)
     , m_zeroTime(0) // 0 is used by unit tests which cannot initialize from the loader
     , m_zeroTimeInitialized(false)
+    , m_outdatedAnimationCount(0)
     , m_playbackRate(1)
     , m_lastCurrentTimeInternal(0)
 {
@@ -147,12 +148,17 @@ void AnimationTimeline::serviceAnimations(TimingUpdateReason reason)
             m_animationsNeedingUpdate.remove(animation);
     }
 
-    ASSERT(!hasOutdatedAnimation());
+    ASSERT(m_outdatedAnimationCount == 0);
+
+#if ENABLE(ASSERT)
+    for (const auto& animation : m_animationsNeedingUpdate)
+        ASSERT(!animation->outdated());
+#endif
 }
 
 void AnimationTimeline::scheduleNextService()
 {
-    ASSERT(!hasOutdatedAnimation());
+    ASSERT(m_outdatedAnimationCount == 0);
 
     double timeToNextEffect = std::numeric_limits<double>::infinity();
     for (const auto& animation : m_animationsNeedingUpdate) {
@@ -262,23 +268,21 @@ void AnimationTimeline::pauseAnimationsForTesting(double pauseTime)
     serviceAnimations(TimingUpdateOnDemand);
 }
 
-bool AnimationTimeline::hasOutdatedAnimation() const
+bool AnimationTimeline::needsAnimationTimingUpdate()
 {
-    for (const auto& animation : m_animationsNeedingUpdate) {
-        if (animation->outdated())
-            return true;
-    }
-    return false;
+    return m_animationsNeedingUpdate.size() && currentTimeInternal() != m_lastCurrentTimeInternal;
 }
 
-bool AnimationTimeline::needsAnimationTimingUpdate()
+void AnimationTimeline::clearOutdatedAnimation(Animation* animation)
 {
-    return m_animationsNeedingUpdate.size() && currentTimeInternal() != m_lastCurrentTimeInternal;
+    ASSERT(!animation->outdated());
+    m_outdatedAnimationCount--;
 }
 
 void AnimationTimeline::setOutdatedAnimation(Animation* animation)
 {
     ASSERT(animation->outdated());
+    m_outdatedAnimationCount++;
     m_animationsNeedingUpdate.add(animation);
     if (m_document && m_document->page() && !m_document->page()->animator().isServicingAnimations())
         m_timing->serviceOnNextFrame();