Extract minimal RenderViewHost interface for embedders, leaving

content/public/browser/render_view_host_observer.cc

Index: content/public/browser/render_view_host_observer.cc
diff --git a/content/public/browser/render_view_host_observer.cc b/content/public/browser/render_view_host_observer.cc
index 720d0046b4e494e2be54cd8cc4780f0ea8fe8d77..a2504c33a65b4c2234d8da5928bc5783c9bcdab6 100644
--- a/content/public/browser/render_view_host_observer.cc
+++ b/content/public/browser/render_view_host_observer.cc
@@ -9,8 +9,8 @@
 namespace content {
 
 RenderViewHostObserver::RenderViewHostObserver(RenderViewHost* render_view_host)
-    : render_view_host_(render_view_host),
-      routing_id_(render_view_host->routing_id()) {
+    : render_view_host_(static_cast<RenderViewHostImpl*>(render_view_host)),
+      routing_id_(render_view_host_->GetRoutingID()) {
   render_view_host_->AddObserver(this);
 }
 
@@ -42,6 +42,10 @@ bool RenderViewHostObserver::Send(IPC::Message* message) {
   return render_view_host_->Send(message);
 }
 
+RenderViewHost* RenderViewHostObserver::render_view_host() const {
+  return render_view_host_;
+}
+
 void RenderViewHostObserver::RenderViewHostDestruction() {
   render_view_host_->RemoveObserver(this);
   RenderViewHost* rvh = render_view_host_;