Web Animations CSS: Unfreeze AnimationClock if sampling timelines does not trigger style recalc

Source/core/animation/TimedItem.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 74 matching lines @@
     Player* player() { return m_player; }
 
     const Timing& specified() const { return m_specified; }
 
 protected:
     TimedItem(const Timing&, PassOwnPtr<EventDelegate> = nullptr);
 
     // When TimedItem receives a new inherited time via updateInheritedTime
     // it will (if necessary) recalculate timings and (if necessary) call
     // updateChildrenAndEffects.
-    void updateInheritedTime(double inheritedTime) const;
+    // Returns whether style recalc was triggered.
+    bool updateInheritedTime(double inheritedTime) const;
 
 private:
-    virtual void updateChildrenAndEffects() const = 0;
+    // Returns whether style recalc was triggered.
+    virtual bool updateChildrenAndEffects() const = 0;
     virtual double intrinsicIterationDuration() const { return 0; };
     virtual void willDetach() = 0;
     virtual double calculateTimeToEffectChange(double inheritedTime, double activeTime, Phase) const = 0;
 
     void attach(Player* player) { m_player = player; };
     void detach()
     {
         ASSERT(m_player);
         willDetach();
         m_player = 0;
@@ skipping 19 matching lines @@
     } m_calculated;
     mutable bool m_isFirstSample;
 
     // FIXME: Should check the version and reinherit time if inconsistent.
     const CalculatedTiming& ensureCalculated() const { return m_calculated; }
 };
 
 } // namespace WebCore
 
 #endif