Inside of content, prefer SiteInstanceImpl to SiteInstance.

content/browser/frame_host/render_frame_proxy_host.cc

Index: content/browser/frame_host/render_frame_proxy_host.cc
diff --git a/content/browser/frame_host/render_frame_proxy_host.cc b/content/browser/frame_host/render_frame_proxy_host.cc
index f4ba295b7add988c7c38c4620db9f4af7ab69cf1..04b4b819068e1809c5d9c87e892e4f279706d5a6 100644
--- a/content/browser/frame_host/render_frame_proxy_host.cc
+++ b/content/browser/frame_host/render_frame_proxy_host.cc
@@ -46,7 +46,7 @@ RenderFrameProxyHost* RenderFrameProxyHost::FromID(int process_id,
   return it == frames->end() ? NULL : it->second;
 }
 
-RenderFrameProxyHost::RenderFrameProxyHost(SiteInstance* site_instance,
+RenderFrameProxyHost::RenderFrameProxyHost(SiteInstanceImpl* site_instance,
                                            RenderViewHostImpl* render_view_host,
                                            FrameTreeNode* frame_tree_node)
     : routing_id_(site_instance->GetProcess()->GetNextRoutingID()),
@@ -268,7 +268,7 @@ void RenderFrameProxyHost::OnRouteMessageEvent(
   // TODO(alexmos, lazyboy):  The check for browser plugin guest currently
   // requires going through the delegate.  It should be refactored and
   // performed here once OOPIF support in <webview> is further along.
-  SiteInstance* target_site_instance = target_rfh->GetSiteInstance();
+  SiteInstanceImpl* target_site_instance = target_rfh->GetSiteInstance();
   if (!target_site_instance->IsRelatedSiteInstance(GetSiteInstance()) &&
       !target_rfh->delegate()->ShouldRouteMessageEvent(target_rfh,
                                                        GetSiteInstance()))