Revert r160071 "Web Animations: Implement AnimationClock and fix start time of animations"

Source/core/dom/Document.h

Index: Source/core/dom/Document.h
diff --git a/Source/core/dom/Document.h b/Source/core/dom/Document.h
index c82c6d85d188bea22a00062b1d3caec9c5364e0e..5e7a9ff02f12bdae189c2f725502f4546d54d907 100644
--- a/Source/core/dom/Document.h
+++ b/Source/core/dom/Document.h
@@ -60,7 +60,6 @@
 namespace WebCore {
 
 class AXObjectCache;
-class AnimationClock;
 class Attr;
 class CDATASection;
 class CSSStyleDeclaration;
@@ -1040,7 +1039,6 @@ public:
     // Return a Locale for the default locale if the argument is null or empty.
     Locale& getCachedLocale(const AtomicString& locale = nullAtom);
 
-    AnimationClock& animationClock() { return *m_animationClock; }
     DocumentTimeline* timeline() const { return m_timeline.get(); }
 
     void addToTopLayer(Element*, const Element* before = 0);
@@ -1382,7 +1380,6 @@ private:
     typedef HashMap<AtomicString, OwnPtr<Locale> > LocaleIdentifierToLocaleMap;
     LocaleIdentifierToLocaleMap m_localeCache;
 
-    OwnPtr<AnimationClock> m_animationClock;
     RefPtr<DocumentTimeline> m_timeline;
 
     RefPtr<Document> m_templateDocument;