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

content/shell/browser/shell_devtools_manager_delegate.cc

 // Copyright 2013 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/shell/browser/shell_devtools_manager_delegate.h"
 
 #include <vector>
 
 #include "base/bind.h"
 #include "base/command_line.h"
@@ skipping 245 matching lines @@
 std::string ShellDevToolsManagerDelegate::GetPageThumbnailData(
     const GURL& url) {
   return std::string();
 }
 
 scoped_ptr<DevToolsTarget>
 ShellDevToolsManagerDelegate::CreateNewTarget(const GURL& url) {
   Shell* shell = Shell::CreateNewWindow(browser_context_,
                                         url,
                                         NULL,
-                                        MSG_ROUTING_NONE,
                                         gfx::Size());
   return scoped_ptr<DevToolsTarget>(
       new Target(DevToolsAgentHost::GetOrCreateFor(shell->web_contents())));
 }
 
 void ShellDevToolsManagerDelegate::EnumerateTargets(TargetCallback callback) {
   TargetList targets;
   for (const auto& agent_host : DevToolsAgentHost::GetOrCreateAll()) {
     targets.push_back(new Target(agent_host));
   }
   callback.Run(targets);
 }
 
 }  // namespace content