Revert of Web Animations: Timeline should not advance during task execution

Source/core/animation/AnimationClock.cpp

Index: Source/core/animation/AnimationClock.cpp
diff --git a/Source/core/animation/AnimationClock.cpp b/Source/core/animation/AnimationClock.cpp
index e9018afca4ddb38ebe1704f8e964d297a9b5e1c1..649220690e67a27adf18592ac5d9a46d000c9ff2 100644
--- a/Source/core/animation/AnimationClock.cpp
+++ b/Source/core/animation/AnimationClock.cpp
@@ -31,52 +31,23 @@
 #include "config.h"
 #include "core/animation/AnimationClock.h"
 
-#include "wtf/CurrentTime.h"
-#include <math.h>
-
-namespace {
-
-// FIXME: This is an approximation of time between frames, used when
-// ticking the animation clock outside of animation frame callbacks.
-// Ideally this would be generated by the compositor.
-const double approximateFrameTime = 1 / 60.0;
-
-}
-
 namespace WebCore {
-
-unsigned AnimationClock::s_currentTask = 0;
 
 void AnimationClock::updateTime(double time)
 {
     if (time > m_time)
         m_time = time;
-    m_currentTask = s_currentTask;
+    m_frozen = true;
 }
 
 double AnimationClock::currentTime()
 {
-    if (m_currentTask != s_currentTask) {
-        const double currentTime = m_monotonicallyIncreasingTime();
-        if (m_time < currentTime) {
-            // Advance to the first estimated frame after the current time.
-            const double frameShift = fmod(currentTime - m_time, approximateFrameTime);
-            const double newTime = currentTime + approximateFrameTime - frameShift;
-            ASSERT(newTime > currentTime);
-            ASSERT(newTime <= currentTime + approximateFrameTime);
-            updateTime(newTime);
-        } else {
-            m_currentTask = s_currentTask;
-        }
+    if (!m_frozen) {
+        double newTime = m_monotonicallyIncreasingTime();
+        if (newTime >= m_time + minTimeBeforeUnsynchronizedAnimationClockTick)
+            m_time = newTime;
     }
     return m_time;
 }
 
-void AnimationClock::resetTimeForTesting()
-{
-    m_time = 0;
-    m_currentTask = 0;
-    s_currentTask = 0;
 }
-
-}