Add ShellDelegate, MediaDelegate and KeyboardUI stubs to mus ash

ash/sysui/pointer_watcher_delegate_mus.h

 // Copyright 2016 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_SYSUI_POINTER_WATCHER_DELEGATE_MUS_H_
 #define ASH_SYSUI_POINTER_WATCHER_DELEGATE_MUS_H_
 
-#include "ash/pointer_watcher_delegate.h"
+#include "ash/common/pointer_watcher_delegate.h"
 #include "base/macros.h"
 
 namespace ash {
 
 // PointerWatcher support on mus via the WindowManagerConnection.
 class PointerWatcherDelegateMus : public PointerWatcherDelegate {
  public:
   PointerWatcherDelegateMus();
   ~PointerWatcherDelegateMus() override;
 
   // PointerWatcherDelegate:
   void AddPointerWatcher(views::PointerWatcher* watcher) override;
   void RemovePointerWatcher(views::PointerWatcher* watcher) override;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(PointerWatcherDelegateMus);
 };
 
 }  // namespace ash
 
 #endif  // ASH_SYSUI_POINTER_WATCHER_DELEGATE_MUS_H_