Add the main frame routing ID to WebContentsDelegate, use it in BackgroundContents.

chrome/browser/tab_contents/background_contents.cc

 // Copyright (c) 2012 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 "chrome/browser/tab_contents/background_contents.h"
 
 #include "chrome/browser/background/background_contents_service.h"
 #include "chrome/browser/chrome_notification_types.h"
 #include "chrome/browser/extensions/chrome_extension_web_contents_observer.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/renderer_preferences_util.h"
 #include "chrome/browser/ui/webui/chrome_web_ui_controller_factory.h"
 #include "chrome/common/url_constants.h"
 #include "content/public/browser/notification_service.h"
 #include "content/public/browser/render_view_host.h"
 #include "content/public/browser/session_storage_namespace.h"
 #include "content/public/browser/site_instance.h"
 #include "content/public/browser/web_contents.h"
 #include "extensions/browser/view_type_utils.h"
 #include "ui/gfx/rect.h"
 
 using content::SiteInstance;
 using content::WebContents;
 
 BackgroundContents::BackgroundContents(
     SiteInstance* site_instance,
     int routing_id,
+    int main_frame_routing_id,
     Delegate* delegate,
     const std::string& partition_id,
     content::SessionStorageNamespace* session_storage_namespace)
     : delegate_(delegate) {
   profile_ = Profile::FromBrowserContext(
       site_instance->GetBrowserContext());
 
   WebContents::CreateParams create_params(profile_, site_instance);
   create_params.routing_id = routing_id;
+  create_params.main_frame_routing_id = main_frame_routing_id;

[Charlie Reis, 2014/12/11 17:48:18]

What about other places that set CreateParams::routing_id?  Will they have a
similar bug?  (Looks like shell.cc might be the only other place from a quick
code search.)

   if (session_storage_namespace) {
     content::SessionStorageNamespaceMap session_storage_namespace_map;
     session_storage_namespace_map.insert(
         std::make_pair(partition_id, session_storage_namespace));
     web_contents_.reset(WebContents::CreateWithSessionStorage(
         create_params, session_storage_namespace_map));
   } else {
     web_contents_.reset(WebContents::Create(create_params));
   }
   extensions::SetViewType(
@@ skipping 104 matching lines @@
     case chrome::NOTIFICATION_PROFILE_DESTROYED:
     case chrome::NOTIFICATION_APP_TERMINATING: {
       delete this;
       break;
     }
     default:
       NOTREACHED() << "Unexpected notification sent.";
       break;
   }
 }