Web Animations: Sort Animations in the AnimationStack

Source/core/animation/DocumentTimeline.cpp

Index: Source/core/animation/DocumentTimeline.cpp
diff --git a/Source/core/animation/DocumentTimeline.cpp b/Source/core/animation/DocumentTimeline.cpp
index 8f2d489bd891828f3c9ebd2944c0b91691bd4f7b..77ef592d566ff005da38639a7d62257444a653db 100644
--- a/Source/core/animation/DocumentTimeline.cpp
+++ b/Source/core/animation/DocumentTimeline.cpp
@@ -80,7 +80,7 @@ AnimationPlayer* DocumentTimeline::createAnimationPlayer(TimedItem* child)
 AnimationPlayer* DocumentTimeline::play(TimedItem* child)
 {
     AnimationPlayer* player = createAnimationPlayer(child);
-    player->setStartTime(currentTime());
+    player->setStartTime(effectiveTime());
     return player;
 }
 
@@ -151,6 +151,12 @@ double DocumentTimeline::currentTime()
     return m_document->animationClock().currentTime() - m_zeroTime;
 }
 
+double DocumentTimeline::effectiveTime()
+{
+    double time = currentTime();
+    return std::isnan(time) ? 0 : time;
+}
+
 void DocumentTimeline::pauseAnimationsForTesting(double pauseTime)
 {
     for (HashSet<RefPtr<AnimationPlayer> >::iterator it = m_playersNeedingUpdate.begin(); it != m_playersNeedingUpdate.end(); ++it)