Web Animations CSS: Start running animations on the compositor

Source/core/animation/Player.h

Index: Source/core/animation/Player.h
diff --git a/Source/core/animation/Player.h b/Source/core/animation/Player.h
index b4b4d81c1a9e7f2a5efb6657b73e4704984a95f0..0283e7a12f45fc666d33ae4c3518dc98093256ff 100644
--- a/Source/core/animation/Player.h
+++ b/Source/core/animation/Player.h
@@ -75,11 +75,16 @@ public:
     // Reflects all pausing, including via pauseForTesting().
     bool pausedInternal() const { return !isNull(m_pauseStartTime); }
 
+    bool maybeStartAnimationOnCompositor();
+    void cancelAnimationOnCompositor();
+
 private:
     Player(DocumentTimeline&, TimedItem*);
     inline double pausedTimeDrift() const;
     inline double currentTimeBeforeDrift() const;
 
+    bool hasActiveAnimationsOnCompositor();
+
     void setPausedImpl(bool);
 
     double m_pauseStartTime;