In WinAura, also kill the Metro viewer process in AttemptExit().

chrome/browser/browser_process_platform_part_winaura.h

 // Copyright (c) 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.
 
 #ifndef CHROME_BROWSER_BROWSER_PROCESS_PLATFORM_PART_WINAURA_H_
 #define CHROME_BROWSER_BROWSER_PROCESS_PLATFORM_PART_WINAURA_H_
 
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
 
 class CommandLine;
 class MetroViewerProcessHost;
 
 class BrowserProcessPlatformPart {
  public:
   BrowserProcessPlatformPart();
   virtual ~BrowserProcessPlatformPart();
 
   // Called after creating the process singleton or when another chrome
   // rendez-vous with this one.
   virtual void PlatformSpecificCommandLineProcessing(
       const CommandLine& command_line);
 
   // Called from BrowserProcessImpl::StartTearDown().
   virtual void StartTearDown();
 
+  // Invoked when the ASH metro viewer process on Windows 8 exits.
   void OnMetroViewerProcessTerminated();
 
+  // Terminates the metro viewer process if there is one.
+  void TerminateMetroViewerProcess();
+
  private:
   // Hosts the channel for the Windows 8 metro viewer process which runs in
   // the ASH environment.
   scoped_ptr<MetroViewerProcessHost> metro_viewer_process_host_;
 
   DISALLOW_COPY_AND_ASSIGN(BrowserProcessPlatformPart);
 };
 
 #endif  // CHROME_BROWSER_BROWSER_PROCESS_PLATFORM_PART_WINAURA_H_