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

content/shell/browser/shell_browser_main_parts.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_browser_main_parts.h"
 
 #include "base/base_switches.h"
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/files/file_path.h"
@@ skipping 106 matching lines @@
 void ShellBrowserMainParts::InitializeBrowserContexts() {
   set_browser_context(new ShellBrowserContext(false, net_log_.get()));
   set_off_the_record_browser_context(
       new ShellBrowserContext(true, net_log_.get()));
 }
 
 void ShellBrowserMainParts::InitializeMessageLoopContext() {
   Shell::CreateNewWindow(browser_context_.get(),
                          GetStartupURL(),
                          NULL,
-                         MSG_ROUTING_NONE,
                          gfx::Size());
 }
 
 void ShellBrowserMainParts::PreMainMessageLoopRun() {
 #if defined(OS_ANDROID)
   if (CommandLine::ForCurrentProcess()->HasSwitch(
           switches::kEnableCrashReporter)) {
     base::FilePath crash_dumps_dir =
         CommandLine::ForCurrentProcess()->GetSwitchValuePath(
             switches::kCrashDumpsDir);
@@ skipping 22 matching lines @@
   return !run_message_loop_;
 }
 
 void ShellBrowserMainParts::PostMainMessageLoopRun() {
   devtools_http_handler_.reset();
   browser_context_.reset();
   off_the_record_browser_context_.reset();
 }
 
 }  // namespace