Hook up ui::Compositor to Display's BeginFrameSource

cc/surfaces/surface_display_output_surface.h

Index: cc/surfaces/surface_display_output_surface.h
diff --git a/cc/surfaces/surface_display_output_surface.h b/cc/surfaces/surface_display_output_surface.h
index cececd3b012e0cf30ac1dc336f0dfd5ce8023456..098a3e18c570cead766a0645e6629e2c1f0b6853 100644
--- a/cc/surfaces/surface_display_output_surface.h
+++ b/cc/surfaces/surface_display_output_surface.h
@@ -33,11 +33,10 @@ class CC_SURFACES_EXPORT SurfaceDisplayOutputSurface
   ~SurfaceDisplayOutputSurface() override;
 
   void set_display_client(OnscreenDisplayClient* display_client) {
+    DCHECK(!display_client_);
     display_client_ = display_client;
   }
   SurfaceFactory* factory() { return &factory_; }
-  void ReceivedVSyncParameters(base::TimeTicks timebase,
-                               base::TimeDelta interval);
 
   // OutputSurface implementation.
   void SwapBuffers(CompositorFrame* frame) override;