Create a new RenderFrameHost per child frame when --site-per-process is enabled.

content/browser/renderer_host/render_view_host_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_BROWSER_RENDERER_HOST_RENDER_VIEW_HOST_IMPL_H_
 #define CONTENT_BROWSER_RENDERER_HOST_RENDER_VIEW_HOST_IMPL_H_
 
 #include <map>
 #include <string>
 #include <vector>
@@ skipping 444 matching lines @@
   static void FilterURL(ChildProcessSecurityPolicyImpl* policy,
                         const RenderProcessHost* process,
                         bool empty_allowed,
                         GURL* url);
 
   // NOTE: Do not add functions that just send an IPC message that are called in
   // one or two places. Have the caller send the IPC message directly (unless
   // the caller places are in different platforms, in which case it's better
   // to keep them consistent).
 
+  // Called to associate this RenderViewHost with the FrameTree given at
+  // construction. See comment about |main_render_frame_host_| for details.
+  void SwapIntoFrameTree(RenderViewHostImpl* old_render_view_host);

[Charlie Reis, 2013/09/11 22:25:04]

I'm having trouble with this contract.  I guess it's because you're putting the
RFH back on the old RVH, but this seems awkward to keep switching ownership.

+
  protected:
   friend class RenderViewHostObserver;
 
   // Add and remove observers for filtering IPC messages.  Clients must be sure
   // to remove the observer before they go away.
   void AddObserver(RenderViewHostObserver* observer);
   void RemoveObserver(RenderViewHostObserver* observer);
 
   // RenderWidgetHost protected overrides.
   virtual void OnUserGesture() OVERRIDE;
@@ skipping 116 matching lines @@
   // TODO(nasko): Remove this accessor once RenderFrameHost moves into the frame
   // tree.
   RenderFrameHostImpl* main_render_frame_host() const;
 
   // Sets whether this RenderViewHost is swapped out in favor of another,
   // and clears any waiting state that is no longer relevant.
   void SetSwappedOut(bool is_swapped_out);
 
   bool CanAccessFilesOfPageState(const PageState& state) const;
 
-  // This is an RenderFrameHost object associated with the top-level frame in
-  // the page rendered by this RenderViewHost.
-  // TODO(nasko): Remove this pointer once we have enough infrastructure to
-  // move this to the top-level FrameTreeNode.
+  // All RenderViewHosts must have a RenderFrameHost for its main frame
+  // thus the RenderFrameHost is created in lock step on construction.
+  // In a WebContents, the FrameTree owns the RenderFrameHost and ownership
+  // is transfered once this RenderViewHost commits.

[Charlie Reis, 2013/09/11 22:25:04]

Is this a temporary thing, such that we should have a TODO saying that it will
go away once we have a RenderFrameHostManager for keeping track of pending RFHs?

[Charlie Reis, 2013/09/24 18:25:58]

Done.

+  //
+  // For standalone RenderViewHosts such as those used by interstitial pages,

[nasko, 2013/09/11 22:26:24]

I wonder if this is going to be true long term. It looks like RenderFrameHost
will take care of painting, so we will have to have one for every
RenderViewHost. Just putting thinking into writing though.

+  // this is the sole reference because there is no FrameTree. Also, when the

[Charlie Reis, 2013/09/11 22:25:04]

I don't think this makes sense.  Interstitial pages can have iframes, right? 
We'll need to somehow support that.

+  // RenderViewHost swaps out, the reference is given back so it can be held in
+  // the swapped out state.
   scoped_ptr<RenderFrameHostImpl> main_render_frame_host_;
 
   // Our delegate, which wants to know about changes in the RenderView.
   RenderViewHostDelegate* delegate_;
 
   // The SiteInstance associated with this RenderViewHost.  All pages drawn
   // in this RenderViewHost are part of this SiteInstance.  Should not change
   // over time.
   scoped_refptr<SiteInstanceImpl> instance_;
 
@@ skipping 96 matching lines @@
   DISALLOW_COPY_AND_ASSIGN(RenderViewHostImpl);
 };
 
 #if defined(COMPILER_MSVC)
 #pragma warning(pop)
 #endif
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_RENDER_VIEW_HOST_IMPL_H_