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

content/browser/web_contents/web_contents_impl.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/browser/web_contents/web_contents_impl.h"
 
 #include <utility>
 
 #include "base/command_line.h"
 #include "base/debug/trace_event.h"
@@ skipping 1487 matching lines @@
       GetBrowserContext(), site_instance.get());
   DOMStorageContextWrapper* dom_storage_context =
       static_cast<DOMStorageContextWrapper*>(partition->GetDOMStorageContext());
   SessionStorageNamespaceImpl* session_storage_namespace_impl =
       static_cast<SessionStorageNamespaceImpl*>(session_storage_namespace);
   CHECK(session_storage_namespace_impl->IsFromContext(dom_storage_context));
 
   if (delegate_ &&
       !delegate_->ShouldCreateWebContents(this,
                                           route_id,
+                                          main_frame_route_id,
                                           params.window_container_type,
                                           params.frame_name,
                                           params.target_url,
                                           partition_id,
                                           session_storage_namespace)) {
     if (route_id != MSG_ROUTING_NONE &&
         !RenderViewHost::FromID(render_process_id, route_id)) {
       // If the embedder didn't create a WebContents for this route, we need to
       // delete the RenderView that had already been created.
       Send(new ViewMsg_Close(route_id));
@@ skipping 2837 matching lines @@
   node->render_manager()->ResumeResponseDeferredAtStart();
 }
 
 void WebContentsImpl::SetForceDisableOverscrollContent(bool force_disable) {
   force_disable_overscroll_content_ = force_disable;
   if (view_)
     view_->SetOverscrollControllerEnabled(CanOverscrollContent());
 }
 
 }  // namespace content