Web Animations: Introduce ActiveAnimations and AnimationStack

Source/core/dom/Element.h

Index: Source/core/dom/Element.h
diff --git a/Source/core/dom/Element.h b/Source/core/dom/Element.h
index 4f71560b17e3cbcbed59c4b3cac0a1de4151a2a9..5bb969c0b7f7222d26e7d94fea09e8e7935681fb 100644
--- a/Source/core/dom/Element.h
+++ b/Source/core/dom/Element.h
@@ -37,7 +37,7 @@
 
 namespace WebCore {
 
-class Animation;
+class ActiveAnimations;
 class Attr;
 class Attribute;
 class ClientRect;
@@ -625,10 +625,9 @@ public:
 
     virtual void reportMemoryUsage(MemoryObjectInfo*) const OVERRIDE;
 
-    void addActiveAnimation(Animation*);
-    void removeActiveAnimation(Animation*);
+    ActiveAnimations* activeAnimations() const;
+    ActiveAnimations* ensureActiveAnimations();
     bool hasActiveAnimations() const;
-    Vector<Animation*>* activeAnimations() const;
 
     InputMethodContext* getInputContext();