Have browser process shutdown metro viewer on Metro -> Metro restart.

chrome/browser/lifetime/application_lifetime_win.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/lifetime/application_lifetime.h"
 
 #include "base/bind.h"
 #include "base/prefs/pref_service.h"
 #include "base/win/metro.h"
 #include "base/win/windows_version.h"
@@ skipping 46 matching lines @@
     prefs->SetString(prefs::kRelaunchMode,
                      upgrade_util::kRelaunchModeDesktop);
   } else {
     prefs->SetString(prefs::kRelaunchMode,
                      upgrade_util::kRelaunchModeMetro);
   }
   AttemptRestart();
 }
 
 #if defined(USE_AURA)
+void MetroExitHelper() {
+  aura::HandleMetroExit();
+}
+
 void ActivateDesktopHelper(AshExecutionStatus ash_execution_status) {
   scoped_ptr<base::Environment> env(base::Environment::Create());
   std::string version_str;
 
   // Get the version variable and remove it from the environment.
   if (!env->GetVar(chrome::kChromeVersionEnvVar, &version_str))
     version_str.clear();
 
   base::FilePath exe_path;
   if (!PathService::Get(base::FILE_EXE, &exe_path))
@@ skipping 25 matching lines @@
 }
 
 void AttemptRestartToMetroMode() {
   PrefService* prefs = g_browser_process->local_state();
   prefs->SetString(prefs::kRelaunchMode,
                    upgrade_util::kRelaunchModeMetro);
   AttemptRestart();
 }
 
 }  // namespace chrome