Make RenderFrame{Host} objects routable.

content/browser/renderer_host/render_view_host_impl.h

Index: content/browser/renderer_host/render_view_host_impl.h
diff --git a/content/browser/renderer_host/render_view_host_impl.h b/content/browser/renderer_host/render_view_host_impl.h
index 20caaf5ea73376ab1123eac26d41f84eb9b3c78b..2ab38188dad9a2e3741e90a18c13c3d853e4d71c 100644
--- a/content/browser/renderer_host/render_view_host_impl.h
+++ b/content/browser/renderer_host/render_view_host_impl.h
@@ -443,6 +443,10 @@ class CONTENT_EXPORT RenderViewHostImpl
     return is_waiting_for_unload_ack_;
   }
 
+  // TODO(nasko): Remove this accessor once RenderFrameHost moves into the frame
+  // tree.
+  RenderFrameHostImpl* main_render_frame_host() const;
+
   // Returns whether the given URL is allowed to commit in the current process.
   // This is a more conservative check than FilterURL, since it will be used to
   // kill processes that commit unauthorized URLs.