Hash iterators: Check for concurrent modification and fix 1 place where it happened

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 77ef592d566ff005da38639a7d62257444a653db..2059351c6e67357ab5abd6a5ed93514843c06070 100644
--- a/Source/core/animation/DocumentTimeline.cpp
+++ b/Source/core/animation/DocumentTimeline.cpp
@@ -98,7 +98,7 @@ void DocumentTimeline::serviceAnimations()
 
     double timeToNextEffect = std::numeric_limits<double>::infinity();
     Vector<AnimationPlayer*> players;
-    for (HashSet<RefPtr<AnimationPlayer> >::iterator it = m_playersNeedingUpdate.begin(); it != m_playersNeedingUpdate.end(); ++it)
+    for (ListHashSet<RefPtr<AnimationPlayer> >::iterator it = m_playersNeedingUpdate.begin(); it != m_playersNeedingUpdate.end(); ++it)
         players.append(it->get());
 
     std::sort(players.begin(), players.end(), AnimationPlayer::hasLowerPriority);
@@ -159,7 +159,7 @@ double DocumentTimeline::effectiveTime()
 
 void DocumentTimeline::pauseAnimationsForTesting(double pauseTime)
 {
-    for (HashSet<RefPtr<AnimationPlayer> >::iterator it = m_playersNeedingUpdate.begin(); it != m_playersNeedingUpdate.end(); ++it)
+    for (ListHashSet<RefPtr<AnimationPlayer> >::iterator it = m_playersNeedingUpdate.begin(); it != m_playersNeedingUpdate.end(); ++it)
         (*it)->pauseForTesting(pauseTime);
     serviceAnimations();
 }
@@ -181,7 +181,7 @@ size_t DocumentTimeline::numberOfActiveAnimationsForTesting() const
     if (isNull(m_zeroTime))
         return 0;
     size_t count = 0;
-    for (HashSet<RefPtr<AnimationPlayer> >::iterator it = m_playersNeedingUpdate.begin(); it != m_playersNeedingUpdate.end(); ++it) {
+    for (ListHashSet<RefPtr<AnimationPlayer> >::const_iterator it = m_playersNeedingUpdate.begin(); it != m_playersNeedingUpdate.end(); ++it) {
         const TimedItem* timedItem = (*it)->source();
         if ((*it)->hasStartTime())
             count += (timedItem && (timedItem->isCurrent() || timedItem->isInEffect()));