RenderWidget: make routing_id be a parameter of the ctor

content/public/renderer/render_view_observer.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/public/renderer/render_view_observer.h"
 
 #include "content/renderer/render_view_impl.h"
 
 namespace content {
 
 RenderViewObserver::RenderViewObserver(RenderView* render_view)
     : render_view_(static_cast<RenderViewImpl*>(render_view)),
       routing_id_(MSG_ROUTING_NONE) {
   // |render_view_| can be null on unit testing or if Observe() is used.
   if (render_view_) {
     routing_id_ = render_view_->GetRoutingID();
-    // TODO(jam/nick): bring this back DCHECK_NE(routing_id_, MSG_ROUTING_NONE);
     render_view_->AddObserver(this);
   }
 }
 
 RenderViewObserver::~RenderViewObserver() {
   if (render_view_)
     render_view_->RemoveObserver(this);
 }
 
 bool RenderViewObserver::OnMessageReceived(const IPC::Message& message) {
@@ skipping 12 matching lines @@
   return render_view_;
 }
 
 void RenderViewObserver::RenderViewGone() {
   render_view_ = nullptr;
 }
 
 void RenderViewObserver::Observe(RenderView* render_view) {
   if (render_view_) {
     render_view_->RemoveObserver(this);
-    routing_id_ = 0;
+    routing_id_ = MSG_ROUTING_NONE;
   }
 
   render_view_ = static_cast<RenderViewImpl*>(render_view);
   if (render_view_) {
     routing_id_ = render_view_->GetRoutingID();
     render_view_->AddObserver(this);
   }
 }
 
 }  // namespace content