diff --git a/dom/animation/PendingPlayerTracker.cpp b/dom/animation/PendingPlayerTracker.cpp
index 7fb7d872b92..efddaf564c0 100644
--- a/dom/animation/PendingPlayerTracker.cpp
+++ b/dom/animation/PendingPlayerTracker.cpp
@@ -13,15 +13,19 @@ using namespace mozilla;
 
 namespace mozilla {
 
-NS_IMPL_CYCLE_COLLECTION(PendingPlayerTracker, mPlayPendingSet, mDocument)
+NS_IMPL_CYCLE_COLLECTION(PendingPlayerTracker,
+                         mPlayPendingSet,
+                         mPausePendingSet,
+                         mDocument)
 
 NS_IMPL_CYCLE_COLLECTION_ROOT_NATIVE(PendingPlayerTracker, AddRef)
 NS_IMPL_CYCLE_COLLECTION_UNROOT_NATIVE(PendingPlayerTracker, Release)
 
 void
-PendingPlayerTracker::AddPlayPending(dom::AnimationPlayer& aPlayer)
+PendingPlayerTracker::AddPending(dom::AnimationPlayer& aPlayer,
+                                 AnimationPlayerSet& aSet)
 {
-  mPlayPendingSet.PutEntry(&aPlayer);
+  aSet.PutEntry(&aPlayer);
 
   // Schedule a paint. Otherwise animations that don't trigger a paint by
   // themselves (e.g. CSS animations with an empty keyframes rule) won't
@@ -30,15 +34,17 @@ PendingPlayerTracker::AddPlayPending(dom::AnimationPlayer& aPlayer)
 }
 
 void
-PendingPlayerTracker::RemovePlayPending(dom::AnimationPlayer& aPlayer)
+PendingPlayerTracker::RemovePending(dom::AnimationPlayer& aPlayer,
+                                    AnimationPlayerSet& aSet)
 {
-  mPlayPendingSet.RemoveEntry(&aPlayer);
+  aSet.RemoveEntry(&aPlayer);
 }
 
 bool
-PendingPlayerTracker::IsWaitingToPlay(dom::AnimationPlayer const& aPlayer) const
+PendingPlayerTracker::IsWaiting(const dom::AnimationPlayer& aPlayer,
+                                const AnimationPlayerSet& aSet) const
 {
-  return mPlayPendingSet.Contains(const_cast<dom::AnimationPlayer*>(&aPlayer));
+  return aSet.Contains(const_cast<dom::AnimationPlayer*>(&aPlayer));
 }
 
 PLDHashOperator
diff --git a/dom/animation/PendingPlayerTracker.h b/dom/animation/PendingPlayerTracker.h
index 9f974dd5ac7..8438f90f1dd 100644
--- a/dom/animation/PendingPlayerTracker.h
+++ b/dom/animation/PendingPlayerTracker.h
@@ -25,13 +25,41 @@ public:
   NS_INLINE_DECL_CYCLE_COLLECTING_NATIVE_REFCOUNTING(PendingPlayerTracker)
   NS_DECL_CYCLE_COLLECTION_NATIVE_CLASS(PendingPlayerTracker)
 
-  void AddPlayPending(dom::AnimationPlayer& aPlayer);
-  void RemovePlayPending(dom::AnimationPlayer& aPlayer);
-  bool IsWaitingToPlay(dom::AnimationPlayer const& aPlayer) const;
+  void AddPlayPending(dom::AnimationPlayer& aPlayer)
+  {
+    MOZ_ASSERT(!IsWaitingToPause(aPlayer),
+               "Player is already waiting to pause");
+    AddPending(aPlayer, mPlayPendingSet);
+  }
+  void RemovePlayPending(dom::AnimationPlayer& aPlayer)
+  {
+    RemovePending(aPlayer, mPlayPendingSet);
+  }
+  bool IsWaitingToPlay(const dom::AnimationPlayer& aPlayer) const
+  {
+    return IsWaiting(aPlayer, mPlayPendingSet);
+  }
+
+  void AddPausePending(dom::AnimationPlayer& aPlayer)
+  {
+    MOZ_ASSERT(!IsWaitingToPlay(aPlayer),
+               "Player is already waiting to play");
+    AddPending(aPlayer, mPausePendingSet);
+  }
+  void RemovePausePending(dom::AnimationPlayer& aPlayer)
+  {
+    RemovePending(aPlayer, mPausePendingSet);
+  }
+  bool IsWaitingToPause(const dom::AnimationPlayer& aPlayer) const
+  {
+    return IsWaiting(aPlayer, mPausePendingSet);
+  }
 
   void StartPendingPlayersOnNextTick(const TimeStamp& aReadyTime);
   void StartPendingPlayersNow();
-  bool HasPendingPlayers() const { return mPlayPendingSet.Count() > 0; }
+  bool HasPendingPlayers() const {
+    return mPlayPendingSet.Count() > 0 || mPausePendingSet.Count() > 0;
+  }
 
 private:
   ~PendingPlayerTracker() { }
@@ -41,7 +69,15 @@ private:
   typedef nsTHashtable<nsRefPtrHashKey<dom::AnimationPlayer>>
     AnimationPlayerSet;
 
+  void AddPending(dom::AnimationPlayer& aPlayer,
+                  AnimationPlayerSet& aSet);
+  void RemovePending(dom::AnimationPlayer& aPlayer,
+                     AnimationPlayerSet& aSet);
+  bool IsWaiting(const dom::AnimationPlayer& aPlayer,
+                 const AnimationPlayerSet& aSet) const;
+
   AnimationPlayerSet mPlayPendingSet;
+  AnimationPlayerSet mPausePendingSet;
   nsCOMPtr<nsIDocument> mDocument;
 };