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

content/public/browser/web_contents_delegate.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 "content/public/browser/web_contents_delegate.h"
 
 #include "base/compiler_specific.h"
 #include "base/logging.h"
 #include "base/memory/singleton.h"
 #include "content/public/browser/render_view_host.h"
@@ skipping 114 matching lines @@
   return true;
 }
 
 bool WebContentsDelegate::OnGoToEntryOffset(int offset) {
   return true;
 }
 
 bool WebContentsDelegate::ShouldCreateWebContents(
     WebContents* web_contents,
     int route_id,
+    int main_frame_route_id,
     WindowContainerType window_container_type,
     const base::string16& frame_name,
     const GURL& target_url,
     const std::string& partition_id,
     SessionStorageNamespace* session_storage_namespace) {
   return true;
 }
 
 JavaScriptDialogManager* WebContentsDelegate::GetJavaScriptDialogManager(
     WebContents* source) {
@@ skipping 69 matching lines @@
 
 bool WebContentsDelegate::IsNeverVisible(WebContents* web_contents) {
   return false;
 }
 
 bool WebContentsDelegate::SaveFrame(const GURL& url, const Referrer& referrer) {
   return false;
 }
 
 }  // namespace content