Revert of Web Animations: Use a single animation clock

third_party/WebKit/Source/core/animation/AnimationTimeline.cpp

Index: third_party/WebKit/Source/core/animation/AnimationTimeline.cpp
diff --git a/third_party/WebKit/Source/core/animation/AnimationTimeline.cpp b/third_party/WebKit/Source/core/animation/AnimationTimeline.cpp
index 6d4e56af05ab9e731b054555fef2e4f8181d2640..eace544522d53851cd4de48436927cb20ba83801 100644
--- a/third_party/WebKit/Source/core/animation/AnimationTimeline.cpp
+++ b/third_party/WebKit/Source/core/animation/AnimationTimeline.cpp
@@ -89,11 +89,6 @@
 {
 }
 
-bool AnimationTimeline::isActive()
-{
-    return m_document && m_document->page();
-}
-
 void AnimationTimeline::animationAttached(Animation& animation)
 {
     ASSERT(animation.timeline() == this);
@@ -150,7 +145,7 @@
     }
 
     ASSERT(m_outdatedAnimationCount == 0);
-    ASSERT(m_lastCurrentTimeInternal == currentTimeInternal() || (std::isnan(currentTimeInternal()) && std::isnan(m_lastCurrentTimeInternal)));
+    ASSERT(m_lastCurrentTimeInternal == currentTimeInternal());
 
 #if ENABLE(ASSERT)
     for (const auto& animation : m_animationsNeedingUpdate)
@@ -214,7 +209,7 @@
 
 double AnimationTimeline::currentTimeInternal(bool& isNull)
 {
-    if (!isActive()) {
+    if (!m_document) {
         isNull = true;
         return std::numeric_limits<double>::quiet_NaN();
     }
@@ -243,7 +238,7 @@
 
 void AnimationTimeline::setCurrentTimeInternal(double currentTime)
 {
-    if (!isActive())
+    if (!document())
         return;
     m_zeroTime = m_playbackRate == 0
         ? currentTime
@@ -278,9 +273,6 @@
     if (currentTimeInternal() == m_lastCurrentTimeInternal)
         return false;
 
-    if (std::isnan(currentTimeInternal()) && std::isnan(m_lastCurrentTimeInternal))
-        return false;
-
     // We allow m_lastCurrentTimeInternal to advance here when there
     // are no animations to allow animations spawned during style
     // recalc to not invalidate this flag.
@@ -301,13 +293,13 @@
     ASSERT(animation->outdated());
     m_outdatedAnimationCount++;
     m_animationsNeedingUpdate.add(animation);
-    if (isActive() && !m_document->page()->animator().isServicingAnimations())
+    if (m_document && m_document->page() && !m_document->page()->animator().isServicingAnimations())
         m_timing->serviceOnNextFrame();
 }
 
 void AnimationTimeline::setPlaybackRate(double playbackRate)
 {
-    if (!isActive())
+    if (!document())
         return;
     double currentTime = currentTimeInternal();
     m_playbackRate = playbackRate;