Add --use-ime-service command line flag to enable InputMethodMus in --mus.

ash/shell.h

 // 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.
 
 #ifndef ASH_SHELL_H_
 #define ASH_SHELL_H_
 
 #include <memory>
 #include <utility>
 #include <vector>
@@ skipping 240 matching lines @@
   }
 
   static void set_window_manager_client(aura::WindowManagerClient* client) {
     window_manager_client_ = client;
   }
   static aura::WindowManagerClient* window_manager_client() {
     return window_manager_client_;
   }
 
   static Config GetAshConfig();
+  static bool UseIMEService();

[sky, 2017/05/05 17:08:08]

'UseIMEService' reads a verb, where as this is information. How about
ShouldUseImeService?

[Hadi, 2017/05/05 17:27:40]

Done.

 
   // Creates a default views::NonClientFrameView for use by windows in the
   // Ash environment.
   views::NonClientFrameView* CreateDefaultNonClientFrameView(
       views::Widget* widget);
 
   // Sets work area insets of the display containing |window|, pings observers.
   void SetDisplayWorkAreaInsets(aura::Window* window,
                                 const gfx::Insets& insets);
 
@@ skipping 538 matching lines @@
   base::ObserverList<ShellObserver> shell_observers_;
 
   scoped_refptr<base::SequencedWorkerPool> blocking_pool_;
 
   DISALLOW_COPY_AND_ASSIGN(Shell);
 };
 
 }  // namespace ash
 
 #endif  // ASH_SHELL_H_