Animations: Introduce compositor AnimationPlayer and AnimationTimeline.

Source/core/page/ChromeClient.h

Index: Source/core/page/ChromeClient.h
diff --git a/Source/core/page/ChromeClient.h b/Source/core/page/ChromeClient.h
index 2a14ea1cf17d637c0985c644c85978492b9ac128..2c50b3343069b93267050884942dff1d495af0d1 100644
--- a/Source/core/page/ChromeClient.h
+++ b/Source/core/page/ChromeClient.h
@@ -61,6 +61,7 @@ class Node;
 class Page;
 class PagePopupDriver;
 class PopupMenuClient;
+class WebCompositorAnimationTimeline;
 
 struct CompositedSelectionBound;
 struct DateTimeChooserParameters;
@@ -180,6 +181,9 @@ public:
     // it sets it for the WebViewImpl.
     virtual void attachRootGraphicsLayer(GraphicsLayer*, LocalFrame* localRoot) = 0;
 
+    virtual void attachCompositorAnimationTimeline(WebCompositorAnimationTimeline*, LocalFrame* localRoot) { }
+    virtual void detachCompositorAnimationTimeline(WebCompositorAnimationTimeline*, LocalFrame* localRoot) { }
+
     virtual void enterFullScreenForElement(Element*) { }
     virtual void exitFullScreenForElement(Element*) { }