Extract minimal RenderViewHost interface for embedders, leaving

content/public/browser/web_contents_observer.cc

Index: content/public/browser/web_contents_observer.cc
diff --git a/content/public/browser/web_contents_observer.cc b/content/public/browser/web_contents_observer.cc
index ecbb3bfd4cf9c9fd10a6478bfd43d647a5e419e2..a6abd79c5a50301446f044104b747e85fdde0b21 100644
--- a/content/public/browser/web_contents_observer.cc
+++ b/content/public/browser/web_contents_observer.cc
@@ -47,14 +47,15 @@ bool WebContentsObserver::Send(IPC::Message* message) {
     return false;
   }
 
-  return tab_contents_->GetRenderViewHost()->Send(message);
+  return static_cast<RenderViewHostImpl*>(
+      tab_contents_->GetRenderViewHost())->Send(message);
 }
 
 int WebContentsObserver::routing_id() const {
   if (!tab_contents_ || !tab_contents_->GetRenderViewHost())
     return MSG_ROUTING_NONE;
 
-  return tab_contents_->GetRenderViewHost()->routing_id();
+  return tab_contents_->GetRenderViewHost()->GetRoutingID();
 }
 
 void WebContentsObserver::TabContentsDestroyed() {