Revert of mus: Rename .*PointerWatcher.* to .*PointerDownWatcher.*.

ash/sysui/pointer_down_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_DOWN_WATCHER_DELEGATE_MUS_H_
-#define ASH_SYSUI_POINTER_DOWN_WATCHER_DELEGATE_MUS_H_
-
-#include "ash/common/pointer_down_watcher_delegate.h"
-#include "base/macros.h"
-
-namespace ash {
-
-// PointerDownWatcher support on mus via the WindowManagerConnection.
-class PointerDownWatcherDelegateMus : public PointerDownWatcherDelegate {
- public:
-  PointerDownWatcherDelegateMus();
-  ~PointerDownWatcherDelegateMus() override;
-
-  // PointerDownWatcherDelegate:
-  void AddPointerDownWatcher(views::PointerDownWatcher* watcher) override;
-  void RemovePointerDownWatcher(views::PointerDownWatcher* watcher) override;
-
- private:
-  DISALLOW_COPY_AND_ASSIGN(PointerDownWatcherDelegateMus);
-};
-
-}  // namespace ash
-
-#endif  // ASH_SYSUI_POINTER_DOWN_WATCHER_DELEGATE_MUS_H_