Add WasShown/WasHidden to RenderFrameObserver.

content/renderer/render_widget.h

Index: content/renderer/render_widget.h
diff --git a/content/renderer/render_widget.h b/content/renderer/render_widget.h
index acdc7d454dbb13922fb1a64b841014e2deb37b06..d5c08d2b5461447d4609a431758d4e468299c18c 100644
--- a/content/renderer/render_widget.h
+++ b/content/renderer/render_widget.h
@@ -113,6 +113,11 @@ class CONTENT_EXPORT RenderWidget
   void RegisterSwappedOutChildFrame(RenderFrameImpl* frame);
   void UnregisterSwappedOutChildFrame(RenderFrameImpl* frame);
 
+  // Functions to track all RenderFrame objects associated with this
+  // RenderWidget.
+  void RegisterRenderFrame(RenderFrameImpl* frame);
+  void UnregisterRenderFrame(RenderFrameImpl* frame);
+
   // IPC::Listener
   virtual bool OnMessageReceived(const IPC::Message& msg) OVERRIDE;
 
@@ -712,6 +717,11 @@ class CONTENT_EXPORT RenderWidget
   // of compositing-related events (e.g. DidCommitCompositorFrame).
   ObserverList<RenderFrameImpl> swapped_out_frames_;
 
+  // A list of RenderFrames associated with this RenderWidget. Notifications
+  // are sent to each frame in the list for events such as changing
+  // visibility state for example.
+  ObserverList<RenderFrameImpl> render_frames_;
+
   ui::MenuSourceType context_menu_source_type_;
   gfx::Point touch_editing_context_menu_location_;