Make RenderFrame(Host) own a RenderWidget(Host).

content/renderer/render_frame_impl.h

Index: content/renderer/render_frame_impl.h
diff --git a/content/renderer/render_frame_impl.h b/content/renderer/render_frame_impl.h
index 7dd28607bc8e79bfcf586d05375299affca118a7..02364df3ad23aa353857eac942619d988126a2ab 100644
--- a/content/renderer/render_frame_impl.h
+++ b/content/renderer/render_frame_impl.h
@@ -505,6 +505,7 @@ class CONTENT_EXPORT RenderFrameImpl
   // content/common/*_messages.h for the message that the function is handling.
   void OnBeforeUnload();
   void OnSwapOut(int proxy_routing_id);
+  void OnNewWidgetForFrame(int routing_id_for_widget, bool hidden);
   void OnStop();
   void OnShowContextMenu(const gfx::Point& location);
   void OnContextMenuClosed(const CustomContextMenuContext& custom_context);
@@ -645,6 +646,10 @@ class CONTENT_EXPORT RenderFrameImpl
   RenderFrameProxy* render_frame_proxy_;
   bool is_detaching_;
 
+  // Used when the RenderFrame is a root of a connected subtree of local

[Charlie Reis, 2014/10/02 00:06:57]

This still doesn't match my understanding.  It sounds like it's only used if all
frames in the subtree are local, but I think we use it if the RenderFrame's
parent is a proxy, regardless of what's in the subtree.

[kenrb, 2014/10/02 20:20:48]

Okay, to be graph theoretically precise I think I would have to say 'root of a
maximal connected subtree of local frames', because then having a local frame as
a parent would mean that a given frame is not such a root. I'll try a different
approach because this makes me think trying to use precise graph terminology
might be too esoteric.

+  // frames.
+  scoped_refptr<RenderWidget> render_widget_;
+
 #if defined(ENABLE_PLUGINS)
   // Current text input composition text. Empty if no composition is in
   // progress.