gfx: Add FrameTime and DisplayTime classes

ui/compositor/compositor_observer.h

Index: ui/compositor/compositor_observer.h
diff --git a/ui/compositor/compositor_observer.h b/ui/compositor/compositor_observer.h
index aced251b3f99d9410c15a714c8b5b1e110fe16b7..68a781fb22c03751f40fa2a5a2df6d3366e5812d 100644
--- a/ui/compositor/compositor_observer.h
+++ b/ui/compositor/compositor_observer.h
@@ -27,7 +27,7 @@ class COMPOSITOR_EXPORT CompositorObserver {
   // Called when compositing started: it has taken all the layer changes into
   // account and has issued the graphics commands.
   virtual void OnCompositingStarted(Compositor* compositor,
-                                    base::TimeTicks start_time) = 0;
+                                    gfx::FrameTime start_time) = 0;
 
   // Called when compositing completes: the present to screen has completed.
   virtual void OnCompositingEnded(Compositor* compositor) = 0;