CC Animation: Introduce some dirty flags to optimize PushProperties on commit

cc/animation/animation_timeline.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CC_ANIMATION_ANIMATION_TIMELINE_H_
 #define CC_ANIMATION_ANIMATION_TIMELINE_H_
 
 #include <memory>
 #include <unordered_map>
 
@@ skipping 28 matching lines @@
 
   void AttachPlayer(scoped_refptr<AnimationPlayer> player);
   void DetachPlayer(scoped_refptr<AnimationPlayer> player);
 
   void ClearPlayers();
 
   void PushPropertiesTo(AnimationTimeline* timeline_impl);
 
   AnimationPlayer* GetPlayerById(int player_id) const;
 
+  void SetNeedsPushProperties();
+  bool needs_push_properties() const { return needs_push_properties_; }
+
  private:
   friend class base::RefCounted<AnimationTimeline>;
 
   explicit AnimationTimeline(int id);
   virtual ~AnimationTimeline();
 
   void PushAttachedPlayersToImplThread(AnimationTimeline* timeline) const;
   void RemoveDetachedPlayersFromImplThread(AnimationTimeline* timeline) const;
   void PushPropertiesToImplThread(AnimationTimeline* timeline);
 
   void ErasePlayer(scoped_refptr<AnimationPlayer> player);
 
   // A list of all players which this timeline owns.
   using IdToPlayerMap = std::unordered_map<int, scoped_refptr<AnimationPlayer>>;
   IdToPlayerMap id_to_player_map_;
 
   int id_;
   AnimationHost* animation_host_;
+  bool needs_push_properties_;
 
   // Impl-only AnimationTimeline has no main thread instance and lives on
   // it's own.
   bool is_impl_only_;
 
   DISALLOW_COPY_AND_ASSIGN(AnimationTimeline);
 };
 
 }  // namespace cc
 
 #endif  // CC_ANIMATION_ANIMATION_TIMELINE_H_