Always create FrameTreeNodes and RenderFrameHosts for every frame.

content/renderer/render_view_impl.h

 // Copyright (c) 2012 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_VIEW_IMPL_H_
 #define CONTENT_RENDERER_RENDER_VIEW_IMPL_H_
 
 #include <deque>
 #include <map>
 #include <set>
@@ skipping 1363 matching lines @@
   // or right" state that was last sent to the browser.
   bool cached_is_main_frame_pinned_to_left_;
   bool cached_is_main_frame_pinned_to_right_;
 
   // These store the "has scrollbars" state last sent to the browser.
   bool cached_has_main_frame_horizontal_scrollbar_;
   bool cached_has_main_frame_vertical_scrollbar_;
 
   // Helper objects ------------------------------------------------------------
 
-  scoped_ptr<RenderFrameImpl> main_render_frame_;
+  // Deleted by RenderFrameImpl::frameDetach().
+  RenderFrameImpl* main_render_frame_;

[awong, 2013/11/22 01:07:15]

I think this still needs to be a scoped_ptr.  See comment in frameDetach()

[Charlie Reis, 2013/11/22 02:07:23]

I'm confused.  Are you referring to this comment?

  // If the frame does not have a parent, it is the main frame. The main
  // frame is owned by the containing RenderViewHost so it does not require
  // any cleanup here.

That comment isn't consistent with what I see in the debugger.  When closing a
tab with an iframe that is sharing a process with another tab, I see calls to
RenderFrameImpl::frameDetach for both the iframe and the main frame.

Indeed, the comments in RenderFrameImpl::frameDetach seem wrong, since
detachFromParent seems to be called for every frame.

 
   RendererWebCookieJarImpl cookie_jar_;
 
   // The next group of objects all implement RenderViewObserver, so are deleted
   // along with the RenderView automatically.  This is why we just store
   // weak references.
 
   // Holds a reference to the service which provides desktop notifications.
   NotificationProvider* notification_provider_;
 
@@ skipping 168 matching lines @@
   // use the Observer interface to filter IPC messages and receive frame change
   // notifications.
   // ---------------------------------------------------------------------------
 
   DISALLOW_COPY_AND_ASSIGN(RenderViewImpl);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_RENDER_VIEW_IMPL_H_