android: Add draw completion for CompositorView

content/public/browser/android/compositor_client.h

Index: content/public/browser/android/compositor_client.h
diff --git a/content/public/browser/android/compositor_client.h b/content/public/browser/android/compositor_client.h
index c6c308d5697715fe75bae67ab76ac588f58d7a67..bb03a251627771b90e9b613f9ab4c0435a91e757 100644
--- a/content/public/browser/android/compositor_client.h
+++ b/content/public/browser/android/compositor_client.h
@@ -15,9 +15,14 @@ class CONTENT_EXPORT CompositorClient {
   // Gives the client a chance to update the layer tree host before compositing.
   virtual void UpdateLayerTreeHost() {}
 
-  // The compositor has completed swapping a frame.
+  // The compositor has completed swapping a frame. This is a subset of
+  // DidSwapBuffers and corresponds only to frames where Compositor submits a
+  // new frame.
   virtual void DidSwapFrame(int pending_frames) {}
 
+  // This is called on all swap buffers, regardless of cause.
+  virtual void DidSwapBuffers() {}
+
  protected:
   CompositorClient() {}
   virtual ~CompositorClient() {}