Web Animations: Timeline should not advance during task execution

Source/core/animation/AnimationClock.h

Index: Source/core/animation/AnimationClock.h
diff --git a/Source/core/animation/AnimationClock.h b/Source/core/animation/AnimationClock.h
index 540dfbeb2ebd126188b648a079d5a337dfb46ee1..b5bb0d9adc6b5e13f1351019755fac8e21661591 100644
--- a/Source/core/animation/AnimationClock.h
+++ b/Source/core/animation/AnimationClock.h
@@ -32,39 +32,33 @@
 #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