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

chrome/browser/browser_process_platform_part_base.cc

 // 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.
 
+#include "base/logging.h"
 #include "chrome/browser/browser_process_platform_part_base.h"
+#include "chrome/browser/lifetime/application_lifetime.h"
 
 BrowserProcessPlatformPartBase::BrowserProcessPlatformPartBase() {
 }
 
 BrowserProcessPlatformPartBase::~BrowserProcessPlatformPartBase() {
 }
 
 void BrowserProcessPlatformPartBase::PlatformSpecificCommandLineProcessing(
     const CommandLine& /* command_line */) {
 }
 
 void BrowserProcessPlatformPartBase::StartTearDown() {
 }
+
+void BrowserProcessPlatformPartBase::AttemptExit() {
+// chrome::CloseAllBrowsers() doesn't link on OS_IOS and OS_ANDROID, but
+// OS_ANDROID overrides this method already and OS_IOS never calls this.
+#if defined(OS_IOS) || defined(OS_ANDROID)
+  NOTREACHED();
+#else
+  // On most platforms, closing all windows causes the application to exit.
+  chrome::CloseAllBrowsers();
+#endif
+}