Make RenderFrameHostManager swap RenderFrameHosts, not RenderViewHosts.

content/browser/frame_host/render_frame_host_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_BROWSER_FRAME_HOST_RENDER_FRAME_HOST_IMPL_H_
 #define CONTENT_BROWSER_FRAME_HOST_RENDER_FRAME_HOST_IMPL_H_
 
 #include <string>
 
 #include "base/compiler_specific.h"
@@ skipping 58 matching lines @@
 
   // IPC Message handlers.
   void OnDetach(int64 parent_frame_id, int64 frame_id);
   void OnDidStartProvisionalLoadForFrame(int64 frame_id,
                                          int64 parent_frame_id,
                                          bool main_frame,
                                          const GURL& url);
 
   bool is_swapped_out() { return is_swapped_out_; }
 
-  // TODO(nasko): This should be removed and replaced by RenderProcessHost.
-  RenderViewHostImpl* render_view_host_;  // Not owned.
+  // For now, RenderFrameHosts indirectly keep RenderViewHosts alive via a
+  // refcount that calls Shutdown when it reaches zero.  This allows each
+  // RenderFrameHostManager to just care about RenderFrameHosts, while ensuring
+  // we have a RenderViewHost for each RenderFrameHost.
+  // TODO(creis): RenderViewHost will eventually go away and be replaced with
+  // some form of page context.
+  RenderViewHostImpl* render_view_host_;
 
   RenderFrameHostDelegate* delegate_;
 
   // Reference to the whole frame tree that this RenderFrameHost belongs too.
   // Allows this RenderFrameHost to add and remove nodes in response to
   // messages from the renderer requesting DOM manipulation.
   FrameTree* frame_tree_;
 
   // The FrameTreeNode which this RenderFrameHostImpl is hosted in.
   FrameTreeNode* frame_tree_node_;
 
   int routing_id_;
   bool is_swapped_out_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderFrameHostImpl);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_FRAME_HOST_RENDER_FRAME_HOST_IMPL_H_