Always create FrameTreeNodes and RenderFrameHosts for every frame.

content/renderer/render_view_impl.cc

 // 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.
 
 #include "content/renderer/render_view_impl.h"
 
 #include <algorithm>
 #include <cmath>
 
 #include "base/auto_reset.h"
@@ skipping 3149 matching lines @@
   // opener after hearing about it from the browser, and the browser does not
   // (yet) care about subframe openers.
   if (is_swapped_out_ || frame->parent())
     return;
 
   // Notify WebContents and all its swapped out RenderViews.
   Send(new ViewHostMsg_DidDisownOpener(routing_id_));
 }
 
 void RenderViewImpl::frameDetached(WebFrame* frame) {
+  // NOTE: We may get here for either the main frame or for subframes.  The
+  // RenderFrameImpl will be deleted immediately after this call for subframes
+  // but not for the main frame, which is kept around in a scoped_ptr.
+
   FOR_EACH_OBSERVER(RenderViewObserver, observers_, FrameDetached(frame));
 }
 
 void RenderViewImpl::willClose(WebFrame* frame) {
   FOR_EACH_OBSERVER(RenderViewObserver, observers_, FrameWillClose(frame));
 }
 
 void RenderViewImpl::didMatchCSS(
     WebFrame* frame,
     const WebVector<WebString>& newly_matching_selectors,
@@ skipping 3499 matching lines @@
   for (size_t i = 0; i < icon_urls.size(); i++) {
     WebURL url = icon_urls[i].iconURL();
     if (!url.isEmpty())
       urls.push_back(FaviconURL(url,
                                 ToFaviconType(icon_urls[i].iconType())));
   }
   SendUpdateFaviconURL(urls);
 }
 
 }  // namespace content