Defer app window appearance until first paint.

content/public/browser/web_contents_observer.h

Index: content/public/browser/web_contents_observer.h
diff --git a/content/public/browser/web_contents_observer.h b/content/public/browser/web_contents_observer.h
index f485de4f6fb6975c4803673143d22ac29fd3f002..fbc5206f1f90af2ef4534942ae83bfe8d38a3774 100644
--- a/content/public/browser/web_contents_observer.h
+++ b/content/public/browser/web_contents_observer.h
@@ -218,6 +218,10 @@ class CONTENT_EXPORT WebContentsObserver : public IPC::Listener,
   virtual void FrameDetached(RenderViewHost* render_view_host,
                              int64 frame_id) {}
 
+  // This method is invoked when the renderer has completed its first paint
+  // after a non-empty layout.
+  virtual void DidFirstVisuallyNonEmptyPaint(int32 page_id) {}
+
   // These two methods correspond to the points in time when the spinner of the
   // tab starts and stops spinning.
   virtual void DidStartLoading(RenderViewHost* render_view_host) {}