Web Animations: Sort Animations in the AnimationStack

Source/core/animation/AnimationPlayer.h

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 79 matching lines @@
     // This should only be used for CSS
     void unpause();
 
     void setOutdated();
     bool outdated() { return m_outdated; }
 
     bool maybeStartAnimationOnCompositor();
     void cancelAnimationOnCompositor();
     bool hasActiveAnimationsOnCompositor();
 
-    static bool hasLowerPriority(AnimationPlayer*, AnimationPlayer*);
+    class SortInfo {
+    public:
+        friend class AnimationPlayer;
+        bool operator<(const SortInfo& other) const;
+    private:
+        SortInfo(unsigned sequenceNumber, double startTime)
+            : m_sequenceNumber(sequenceNumber)
+            , m_startTime(startTime)
+        { }
+        unsigned m_sequenceNumber;
+        double m_startTime;
+    };
+
+    const SortInfo& sortInfo() const { return m_sortInfo; }
+
+    static bool hasLowerPriority(AnimationPlayer* player1, AnimationPlayer* player2)
+    {
+        return player1->sortInfo() < player2->sortInfo();
+    }
 
 private:
     AnimationPlayer(DocumentTimeline&, TimedItem*);
     double sourceEnd() const;
     bool limited(double currentTime) const;
     double currentTimeWithoutLag() const;
     double currentTimeWithLag() const;
     void updateTimingState(double newCurrentTime);
     void updateCurrentTimingState();
 
     double m_playbackRate;
     double m_startTime;
     double m_holdTime;
     double m_storedTimeLag;
 
+    SortInfo m_sortInfo;
+
     RefPtr<TimedItem> m_content;
     // FIXME: We should keep the timeline alive and have this as non-null
     // but this is tricky to do without Oilpan
     DocumentTimeline* m_timeline;
     // Reflects all pausing, including via pauseForTesting().
     bool m_paused;
     bool m_held;
     bool m_isPausedForTesting;
 
     // This indicates timing information relevant to the player has changed by
     // means other than the ordinary progression of time
     bool m_outdated;
-
-    unsigned m_sequenceNumber;
 };
 
 } // namespace
 
 #endif