Add a way to schedule generic per-frame events through Document.

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 601792e84557023048ea8e986e1d36f1fa1bbb7b..f4c36f063b968de32c6a6a9e464aea4800fe3a56 100644
--- a/Source/core/dom/Document.h
+++ b/Source/core/dom/Document.h
@@ -911,6 +911,8 @@ public:
     void enqueueResizeEvent();
     void enqueueScrollEventForNode(Node*);
     void enqueueAnimationFrameEvent(PassRefPtrWillBeRawPtr<Event>);
+    // Only one event for a target/event type combination will be dispatched per frame.
+    void enqueueUniqueAnimationFrameEvent(PassRefPtrWillBeRawPtr<Event>);
     void enqueueMediaQueryChangeListeners(WillBeHeapVector<RefPtrWillBeMember<MediaQueryListListener> >&);
 
     bool hasFullscreenElementStack() const { return m_hasFullscreenElementStack; }