aura-mus: add a drag representation image.

ui/aura/mus/window_tree_client.h

 // Copyright 2014 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_AURA_MUS_WINDOW_TREE_CLIENT_H_
 #define UI_AURA_MUS_WINDOW_TREE_CLIENT_H_
 
 #include <stdint.h>
 
 #include <map>
@@ skipping 403 matching lines @@
       const base::Optional<std::vector<uint8_t>>& transit_data) override;
   void WmSetModalType(Id window_id, ui::ModalType type) override;
   void WmSetCanFocus(Id window_id, bool can_focus) override;
   void WmCreateTopLevelWindow(
       uint32_t change_id,
       ClientSpecificId requesting_client_id,
       const std::unordered_map<std::string, std::vector<uint8_t>>&
           transport_properties) override;
   void WmClientJankinessChanged(ClientSpecificId client_id,
                                 bool janky) override;
+  void WmBuildDragImage(const gfx::Point& cursor_location,
+                        const SkBitmap& drag_image,
+                        const gfx::Vector2d& drag_image_offset,
+                        ui::mojom::DragEventSource source) override;
+  void WmMoveDragImage(const gfx::Point& cursor_location,
+                       const WmMoveDragImageCallback& callback) override;
+  void WmDestroyDragImage() override;
   void WmPerformMoveLoop(uint32_t change_id,
                          Id window_id,
                          ui::mojom::MoveLoopSource source,
                          const gfx::Point& cursor_location) override;
   void WmCancelMoveLoop(uint32_t window_id) override;
   void WmDeactivateWindow(Id window_id) override;
   void WmStackAbove(uint32_t change_id, Id above_id, Id below_id) override;
   void WmStackAtTop(uint32_t change_id, uint32_t window_id) override;
   void OnAccelerator(uint32_t ack_id,
                      uint32_t accelerator_id,
@@ skipping 144 matching lines @@
   // ContextFactory that was set on Env originally.
   ui::ContextFactory* initial_context_factory_ = nullptr;
   base::WeakPtrFactory<WindowTreeClient> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(WindowTreeClient);
 };
 
 }  // namespace aura
 
 #endif  // UI_AURA_MUS_WINDOW_TREE_CLIENT_H_