Web Animations: Timeline should not advance during task execution

Source/core/animation/AnimationClock.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 14 matching lines @@
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #ifndef AnimationClock_h
 #define AnimationClock_h
 
 #include "wtf/CurrentTime.h"
+#include "wtf/Noncopyable.h"
 #include "wtf/PassOwnPtr.h"
+#include <limits>
 
 namespace WebCore {
 
-// FIXME: This value is used to suppress updates when time is required outside of a frame.
-// The purpose of allowing the clock to update during such periods is to allow animations
-// to have an appropriate start time and for getComputedStyle to attempt to catch-up to a
-// compositor animation. However a more accurate system might be to attempt to phase-lock
-// with the frame clock.
-const double minTimeBeforeUnsynchronizedAnimationClockTick = 0.005;
-
 class AnimationClock {
+    WTF_MAKE_NONCOPYABLE(AnimationClock);
 public:
-    static PassOwnPtr<AnimationClock> create(WTF::TimeFunction monotonicallyIncreasingTime = WTF::monotonicallyIncreasingTime)
+    explicit AnimationClock(WTF::TimeFunction monotonicallyIncreasingTime = WTF::monotonicallyIncreasingTime)
+        : m_monotonicallyIncreasingTime(monotonicallyIncreasingTime)
+        , m_time(0)
+        , m_currentTask(std::numeric_limits<unsigned>::max())
     {
-        return adoptPtr(new AnimationClock(monotonicallyIncreasingTime));
     }
 
     void updateTime(double time);
     double currentTime();
-    void unfreeze() { m_frozen = false; }
-    void resetTimeForTesting() { m_time = 0; m_frozen = true; }
+    void resetTimeForTesting();
+
+    static void notifyTaskStart() { ++s_currentTask; }
 
 private:
-    AnimationClock(WTF::TimeFunction monotonicallyIncreasingTime)
-        : m_monotonicallyIncreasingTime(monotonicallyIncreasingTime)
-        , m_time(0)
-        , m_frozen(false)
-    {
-    }
     WTF::TimeFunction m_monotonicallyIncreasingTime;
     double m_time;
-    bool m_frozen;
+    unsigned m_currentTask;
+    static unsigned s_currentTask;
 };
 
 } // namespace WebCore
 
 #endif // AnimationClock_h