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

content/renderer/render_frame_impl.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_RENDERER_RENDER_FRAME_IMPL_H_
 #define CONTENT_RENDERER_RENDER_FRAME_IMPL_H_
 
 #include <vector>
 
 #include "base/basictypes.h"
@@ skipping 481 matching lines @@
   // Gets the focused element. If no such element exists then the element will
   // be NULL.
   blink::WebElement GetFocusedElement();
 
   // IPC message handlers ------------------------------------------------------
   //
   // The documentation for these functions should be in
   // 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);
   void OnCustomContextMenuAction(const CustomContextMenuContext& custom_context,
                                  unsigned action);
   void OnUndo();
   void OnRedo();
   void OnCut();
   void OnCopy();
   void OnPaste();
@@ skipping 119 matching lines @@
 
   base::WeakPtr<RenderViewImpl> render_view_;
   int routing_id_;
   bool is_swapped_out_;
   // RenderFrameProxy exists only when is_swapped_out_ is true.
   // TODO(nasko): This can be removed once we don't have a swapped out state on
   // RenderFrame. See https://crbug.com/357747.
   RenderFrameProxy* render_frame_proxy_;
   bool is_detaching_;
 
+  // Used when the RenderFrame is a root of a subtree of local frames.

[nasko, 2014/10/01 16:37:14]

nit: the subtree needn't all be local frames, right? We can have
Remote->(this)Local->Remote and we will still need a widget for this frame. If
the parent is remote, then we need a widget, right?

[kenrb, 2014/10/01 19:27:51]

Okay. Changed 'subtree' to 'connected subtree'.

+  scoped_refptr<RenderWidget> render_widget_;
+
 #if defined(ENABLE_PLUGINS)
   // Current text input composition text. Empty if no composition is in
   // progress.
   base::string16 pepper_composition_text_;
 #endif
 
   RendererWebCookieJarImpl cookie_jar_;
 
   // All the registered observers.
   ObserverList<RenderFrameObserver> observers_;
@@ skipping 97 matching lines @@
 #endif
 
   base::WeakPtrFactory<RenderFrameImpl> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderFrameImpl);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_RENDER_FRAME_IMPL_H_