Removes code using mus client lib

ui/views/mus/drag_drop_client_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 UI_VIEWS_MUS_DRAG_DROP_CLIENT_MUS_H_
-#define UI_VIEWS_MUS_DRAG_DROP_CLIENT_MUS_H_
-
-#include "base/callback.h"
-#include "ui/aura/client/drag_drop_client.h"
-#include "ui/base/dragdrop/drag_drop_types.h"
-
-namespace aura {
-class Window;
-}
-
-namespace ui {
-class OSExchangeData;
-class Window;
-}
-
-namespace views {
-
-// An aura client object that translates aura dragging methods to their
-// remote ui::Window equivalents.
-class DragDropClientMus : public aura::client::DragDropClient {
- public:
-  DragDropClientMus(ui::Window* ui_window);
-  ~DragDropClientMus() override;
-
-  // Overridden from aura::client::DragDropClient:
-  int StartDragAndDrop(const ui::OSExchangeData& data,
-                       aura::Window* root_window,
-                       aura::Window* source_window,
-                       const gfx::Point& screen_location,
-                       int drag_operations,
-                       ui::DragDropTypes::DragEventSource source) override;
-  void DragCancel() override;
-  bool IsDragDropInProgress() override;
-
- private:
-  // Callback for StartDragAndDrop().
-  void OnMoveLoopEnd(bool* out_success,
-                     uint32_t* out_action,
-                     bool in_success,
-                     uint32_t in_action);
-
-  ui::Window* ui_window_;
-
-  base::Closure runloop_quit_closure_;
-
-  DISALLOW_COPY_AND_ASSIGN(DragDropClientMus);
-};
-
-}  // namespace views
-
-#endif  // UI_VIEWS_MUS_DRAG_DROP_CLIENT_MUS_H_