aura: Require explicit ownership of the Env instance.

ash/shell/content_client/shell_browser_main_parts.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 "ash/shell/content_client/shell_browser_main_parts.h"
 
 #include "ash/ash_switches.h"
 #include "ash/desktop_background/desktop_background_controller.h"
 #include "ash/shell.h"
 #include "ash/shell/shell_delegate_impl.h"
@@ skipping 139 matching lines @@
   delegate_ = NULL;
   ash::Shell::DeleteInstance();
   // The global message center state must be shutdown absent
   // g_browser_process.
   message_center::MessageCenter::Shutdown();
 
 #if defined(OS_CHROMEOS)
   chromeos::CrasAudioHandler::Shutdown();
 #endif
 
-  aura::Env::DeleteInstance();
-
   views_delegate_.reset();
 
   // The keyboard may have created a WebContents. The WebContents is destroyed
   // with the UI, and it needs the BrowserContext to be alive during its
   // destruction. So destroy all of the UI elements before destroying the
   // browser context.
   browser_context_.reset();
 }
 
 bool ShellBrowserMainParts::MainMessageLoopRun(int* result_code) {
   base::MessageLoopForUI::current()->Run();
   return true;
 }
 
 }  // namespace shell
 }  // namespace ash