Web Animations: Compositor timeOffset should not be scaled

Source/core/animation/AnimationPlayer.cpp

 /*
  * 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 19 matching lines @@
 
 #include "config.h"
 #include "core/animation/AnimationPlayer.h"
 
 #include "core/animation/Animation.h"
 #include "core/animation/AnimationTimeline.h"
 #include "core/dom/Document.h"
 #include "core/events/AnimationPlayerEvent.h"
 #include "core/frame/UseCounter.h"
 #include "platform/TraceEvent.h"
+#include "wtf/MathExtras.h"
 
 namespace blink {
 
 namespace {
 
 static unsigned nextSequenceNumber()
 {
     static unsigned next = 0;
     return ++next;
 }
@@ skipping 540 matching lines @@
 
 void AnimationPlayer::setOutdated()
 {
     m_outdated = true;
     if (m_timeline)
         m_timeline->setOutdatedAnimationPlayer(this);
 }
 
 bool AnimationPlayer::canStartAnimationOnCompositor()
 {
-    if (m_playbackRate == 0)
+    if (m_playbackRate == 0 || (std::isinf(sourceEnd()) && m_playbackRate < 0))
         return false;
 
     return m_timeline && m_content && m_content->isAnimation() && playing();
 }
 
 bool AnimationPlayer::maybeStartAnimationOnCompositor()
 {
     if (!canStartAnimationOnCompositor())
         return false;
 
     double startTime = timeline()->zeroTime() + startTimeInternal();
     double timeOffset = 0;
     if (std::isnan(startTime)) {
         timeOffset = m_playbackRate < 0 ? sourceEnd() - currentTimeInternal() : currentTimeInternal();
+        timeOffset = timeOffset / fabs(m_playbackRate);
     }
     return toAnimation(m_content.get())->maybeStartAnimationOnCompositor(startTime, timeOffset, m_playbackRate);
 }
 
 void AnimationPlayer::setCompositorPending(bool sourceChanged)
 {
     // FIXME: Animation could notify this directly?
     if (!hasActiveAnimationsOnCompositor()) {
         m_compositorState.release();
     }
@@ skipping 185 matching lines @@
 
 void AnimationPlayer::trace(Visitor* visitor)
 {
     visitor->trace(m_content);
     visitor->trace(m_timeline);
     visitor->trace(m_pendingFinishedEvent);
     EventTargetWithInlineData::trace(visitor);
 }
 
 } // namespace