Mus+Ash: Use standard cc mechanism for surface lifetime.

services/ui/ws/platform_display_delegate.h

Index: services/ui/ws/platform_display_delegate.h
diff --git a/services/ui/ws/platform_display_delegate.h b/services/ui/ws/platform_display_delegate.h
index f0dfa13a55baf76d33a39b52905194bd9b4d5f74..224e79ebcbee371b7579ffb480eceb464ae8cc6a 100644
--- a/services/ui/ws/platform_display_delegate.h
+++ b/services/ui/ws/platform_display_delegate.h
@@ -42,9 +42,6 @@ class PlatformDisplayDelegate {
   virtual void OnViewportMetricsChanged(const ViewportMetrics& old_metrics,
                                         const ViewportMetrics& new_metrics) = 0;
 
-  // Called when a compositor frame is finished drawing.
-  virtual void OnCompositorFrameDrawn() = 0;
-
  protected:
   virtual ~PlatformDisplayDelegate() {}
 };