Update WindowManagerApplication teardown

ash/mus/window_manager_application.cc

 // Copyright 2015 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/mus/window_manager_application.h"
 
 #include <utility>
 
 #include "ash/mojo_interface_factory.h"
 #include "ash/mus/network_connect_delegate_mus.h"
@@ skipping 20 matching lines @@
 #include "ui/events/event.h"
 #include "ui/message_center/message_center.h"
 #include "ui/views/mus/aura_init.h"
 
 namespace ash {
 namespace mus {
 
 WindowManagerApplication::WindowManagerApplication() {}
 
 WindowManagerApplication::~WindowManagerApplication() {
+  // Verify that we created a WindowManager before attempting to tear everything
+  // down. In some fast running tests OnStart may never have been called.
+  if (!window_manager_.get())
+    return;
+
   // Destroy the WindowManager while still valid. This way we ensure
   // OnWillDestroyRootWindowController() is called (if it hasn't been already).
   window_manager_.reset();
 
   if (blocking_pool_) {
     // Like BrowserThreadImpl, the goal is to make it impossible for ash to
     // 'infinite loop' during shutdown, but to reasonably expect that all
     // BLOCKING_SHUTDOWN tasks queued during shutdown get run. There's nothing
     // particularly scientific about the number chosen.
     const int kMaxNewShutdownBlockingTasks = 1000;
@@ skipping 88 matching lines @@
 void WindowManagerApplication::OnBindInterface(
     const service_manager::ServiceInfo& source_info,
     const std::string& interface_name,
     mojo::ScopedMessagePipeHandle interface_pipe) {
   registry_.BindInterface(source_info.identity, interface_name,
                           std::move(interface_pipe));
 }
 
 }  // namespace mus
 }  // namespace ash