Read compositor VSync information from platform, when possible

ui/compositor/compositor.h

Index: ui/compositor/compositor.h
diff --git a/ui/compositor/compositor.h b/ui/compositor/compositor.h
index 81363ba1cb68d3558216bd6e86dbc3f0acc272f2..84ed365803cb7a9b46ee53045325e7df067a238a 100644
--- a/ui/compositor/compositor.h
+++ b/ui/compositor/compositor.h
@@ -43,6 +43,7 @@ class Size;
 namespace ui {
 
 class Compositor;
+class CompositorVSyncManager;
 class Layer;
 class PostedSwapQueue;
 class Reflector;
@@ -163,8 +164,7 @@ class COMPOSITOR_EXPORT CompositorLock
 // view hierarchy.
 class COMPOSITOR_EXPORT Compositor
     : NON_EXPORTED_BASE(public cc::LayerTreeHostClient),
-      NON_EXPORTED_BASE(public cc::LayerTreeHostSingleThreadClient),
-      public base::SupportsWeakPtr<Compositor> {
+      NON_EXPORTED_BASE(public cc::LayerTreeHostSingleThreadClient) {
  public:
   explicit Compositor(gfx::AcceleratedWidget widget);
   virtual ~Compositor();
@@ -222,6 +222,9 @@ class COMPOSITOR_EXPORT Compositor
   // Returns the widget for this compositor.
   gfx::AcceleratedWidget widget() const { return widget_; }
 
+  // Returns the vsync manager for this compositor.
+  scoped_refptr<CompositorVSyncManager> vsync_manager() const;
+
   // Compositor does not own observers. It is the responsibility of the
   // observer to remove itself when it is done observing.
   void AddObserver(CompositorObserver* observer);
@@ -244,9 +247,6 @@ class COMPOSITOR_EXPORT Compositor
   // Signals swap has aborted (e.g. lost context).
   void OnSwapBuffersAborted();
 
-  void OnUpdateVSyncParameters(base::TimeTicks timebase,
-                               base::TimeDelta interval);
-
   // LayerTreeHostClient implementation.
   virtual void WillBeginMainFrame(int frame_id) OVERRIDE {}
   virtual void DidBeginMainFrame() OVERRIDE {}
@@ -302,6 +302,9 @@ class COMPOSITOR_EXPORT Compositor
   scoped_refptr<cc::Layer> root_web_layer_;
   scoped_ptr<cc::LayerTreeHost> host_;
 
+  // The manager of vsync parameters for this compositor.
+  scoped_refptr<CompositorVSyncManager> vsync_manager_;
+
   // Used to verify that we have at most one draw swap in flight.
   scoped_ptr<PostedSwapQueue> posted_swaps_;