Add ShellIntegration::ActivateMetroChrome, which launches Chrome in metro-mode on Windows 8.

chrome/browser/shell_integration.h

 // 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.
 
 #ifndef CHROME_BROWSER_SHELL_INTEGRATION_H_
 #define CHROME_BROWSER_SHELL_INTEGRATION_H_
 #pragma once
 
 #include <string>
 
@@ skipping 106 matching lines @@
   // chrome::kBrowserAppID as app_name.
   static string16 GetChromiumAppId(const FilePath& profile_path);
 
   // Returns the path to the Chromium icon. This is used to specify the icon
   // to use for the taskbar group on Win 7.
   static string16 GetChromiumIconPath();
 
   // Migrates existing chrome shortcuts by tagging them with correct app id.
   // see http://crbug.com/28104
   static void MigrateChromiumShortcuts();
+
+  // Activates Chrome in metro-mode on Windows 8.  Returns false if called on
+  // earlier versions of Windows, if called from within metro-mode, if Chrome
+  // is not the default browser, or if an actual error occurs.
+  static bool ActivateMetroChrome();
 #endif  // defined(OS_WIN)
 
   // The current default web client application UI state. This is used when
   // querying if Chrome is the default browser or the default handler
   // application for a url protocol, and communicates the state and result of
   // a request.
   enum DefaultWebClientUIState {
     STATE_PROCESSING,
     STATE_NOT_DEFAULT,
     STATE_IS_DEFAULT,
@@ skipping 118 matching lines @@
     // Set Chrome as the default handler for this protocol.
     virtual void SetAsDefault() OVERRIDE;
 
     std::string protocol_;
 
     DISALLOW_COPY_AND_ASSIGN(DefaultProtocolClientWorker);
   };
 };
 
 #endif  // CHROME_BROWSER_SHELL_INTEGRATION_H_