Remove usage of RenderViewHost which aren't needed anymore.

content/browser/frame_host/frame_tree.cc

Index: content/browser/frame_host/frame_tree.cc
diff --git a/content/browser/frame_host/frame_tree.cc b/content/browser/frame_host/frame_tree.cc
index 96890f09075d9e438e750271b3405f8ae3b2d80f..eb6725eacd9da5c2b51f13972917994f0725c710 100644
--- a/content/browser/frame_host/frame_tree.cc
+++ b/content/browser/frame_host/frame_tree.cc
@@ -299,8 +299,7 @@ RenderViewHostImpl* FrameTree::GetRenderViewHost(SiteInstance* site_instance) {
 
 void FrameTree::RegisterRenderFrameHost(
     RenderFrameHostImpl* render_frame_host) {
-  SiteInstance* site_instance =
-      render_frame_host->render_view_host()->GetSiteInstance();
+  SiteInstance* site_instance = render_frame_host->GetSiteInstance();
   RenderViewHostMap::iterator iter =
       render_view_host_map_.find(site_instance->GetId());
   CHECK(iter != render_view_host_map_.end());
@@ -310,8 +309,7 @@ void FrameTree::RegisterRenderFrameHost(
 
 void FrameTree::UnregisterRenderFrameHost(
     RenderFrameHostImpl* render_frame_host) {
-  SiteInstance* site_instance =
-      render_frame_host->render_view_host()->GetSiteInstance();
+  SiteInstance* site_instance = render_frame_host->GetSiteInstance();
   int32 site_instance_id = site_instance->GetId();
   RenderViewHostMap::iterator iter =
       render_view_host_map_.find(site_instance_id);