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

content/shell/browser/shell_devtools_frontend.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_frontend.h"
 
 #include "base/command_line.h"
 #include "base/json/json_reader.h"
 #include "base/json/json_writer.h"
 #include "base/strings/string_number_conversions.h"
@@ skipping 16 matching lines @@
 namespace content {
 
 // static
 ShellDevToolsFrontend* ShellDevToolsFrontend::Show(
     WebContents* inspected_contents) {
   scoped_refptr<DevToolsAgentHost> agent(
       DevToolsAgentHost::GetOrCreateFor(inspected_contents));
   Shell* shell = Shell::CreateNewWindow(inspected_contents->GetBrowserContext(),
                                         GURL(),
                                         NULL,
-                                        MSG_ROUTING_NONE,
                                         gfx::Size());
   ShellDevToolsFrontend* devtools_frontend = new ShellDevToolsFrontend(
       shell,
       agent.get());
 
   DevToolsHttpHandler* http_handler = ShellContentBrowserClient::Get()
                                           ->shell_browser_main_parts()
                                           ->devtools_http_handler();
   shell->LoadURL(http_handler->GetFrontendURL("/devtools/devtools.html"));
 
@@ skipping 88 matching lines @@
   base::string16 javascript = base::UTF8ToUTF16(code);
   web_contents()->GetMainFrame()->ExecuteJavaScript(javascript);
 }
 
 void ShellDevToolsFrontend::AgentHostClosed(
     DevToolsAgentHost* agent_host, bool replaced) {
   frontend_shell_->Close();
 }
 
 }  // namespace content