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

chrome/browser/prerender/prerender_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/prerender/prerender_contents.h"
 
 #include <algorithm>
 #include <functional>
 #include <utility>
 
@@ skipping 132 matching lines @@
                    const std::string& request_method,
                    const base::Callback<void(bool)>& callback) override {
     prerender_contents_->Destroy(FINAL_STATUS_DOWNLOAD);
     // Cancel the download.
     callback.Run(false);
   }
 
   bool 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) override {
     // Since we don't want to permit child windows that would have a
     // window.opener property, terminate prerendering.
     prerender_contents_->Destroy(FINAL_STATUS_CREATE_NEW_WINDOW);
     // Cancel the popup.
     return false;
@@ skipping 720 matching lines @@
  void PrerenderContents::AddResourceThrottle(
      const base::WeakPtr<PrerenderResourceThrottle>& throttle) {
    resource_throttles_.push_back(throttle);
  }
 
  void PrerenderContents::AddNetworkBytes(int64 bytes) {
    network_bytes_ += bytes;
  }
 
 }  // namespace prerender