Animations: Allow document animation timelines to have a playback rate

Source/core/animation/AnimationTimeline.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 45 matching lines @@
 
 
 PassRefPtrWillBeRawPtr<AnimationTimeline> AnimationTimeline::create(Document* document, PassOwnPtrWillBeRawPtr<PlatformTiming> timing)
 {
     return adoptRefWillBeNoop(new AnimationTimeline(document, timing));
 }
 
 AnimationTimeline::AnimationTimeline(Document* document, PassOwnPtrWillBeRawPtr<PlatformTiming> timing)
     : m_document(document)
     , m_zeroTime(0)
+    , m_currentTimeSnapshot(0)
+    , m_rawCurrentTimeSnapshot(0)
+    , m_playbackRate(1)
 {
     if (!timing)
         m_timing = adoptPtrWillBeNoop(new AnimationTimelineTiming(this));
     else
         m_timing = timing;
 
     ASSERT(document);
 }
 
 AnimationTimeline::~AnimationTimeline()
@@ skipping 101 matching lines @@
 {
     return currentTimeInternal(isNull) * 1000;
 }
 
 double AnimationTimeline::currentTimeInternal(bool& isNull)
 {
     if (!m_document) {
         isNull = true;
         return std::numeric_limits<double>::quiet_NaN();
     }
-    double result = m_document->animationClock().currentTime() - zeroTime();
+    // New currentTime = currentTime when the playback rate was last changed + time delta since then * playback rate
+    double result = m_currentTimeSnapshot + (m_document->animationClock().currentTime() - m_rawCurrentTimeSnapshot - zeroTime()) * playbackRate();
     isNull = std::isnan(result);
     return result;
 }
 
 double AnimationTimeline::currentTime()
 {
     return currentTimeInternal() * 1000;
 }
 
 double AnimationTimeline::currentTimeInternal()
@@ skipping 25 matching lines @@
 }
 
 void AnimationTimeline::setOutdatedAnimationPlayer(AnimationPlayer* player)
 {
     ASSERT(player->outdated());
     m_playersNeedingUpdate.add(player);
     if (m_document && m_document->page() && !m_document->page()->animator().isServicingAnimations())
         m_timing->serviceOnNextFrame();
 }
 
+void AnimationTimeline::setPlaybackRate(double playbackRate)
+{
+    // FIXME: need to invalidate compositor animations
+    m_currentTimeSnapshot = currentTimeInternal();
+    m_rawCurrentTimeSnapshot = m_document->animationClock().currentTime() - zeroTime();
+    m_playbackRate = playbackRate;
+}
+
+double AnimationTimeline::playbackRate() const
+{
+    return m_playbackRate;
+}
+
 #if !ENABLE(OILPAN)
 void AnimationTimeline::detachFromDocument()
 {
     // FIXME: AnimationTimeline should keep Document alive.
     m_document = nullptr;
 }
 #endif
 
 void AnimationTimeline::trace(Visitor* visitor)
 {
 #if ENABLE(OILPAN)
     visitor->trace(m_document);
     visitor->trace(m_timing);
     visitor->trace(m_playersNeedingUpdate);
     visitor->trace(m_players);
 #endif
 }
 
 } // namespace