mus drag and drop: Add API to let the client cancel the drag.

services/ui/public/cpp/tests/test_window_tree.h

 // Copyright 2015 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 SERVICES_UI_PUBLIC_CPP_TESTS_TEST_WINDOW_TREE_H_
 #define SERVICES_UI_PUBLIC_CPP_TESTS_TEST_WINDOW_TREE_H_
 
 #include <stdint.h>
 
 #include <set>
@@ skipping 90 matching lines @@
   void GetWindowManagerClient(
       mojo::AssociatedInterfaceRequest<mojom::WindowManagerClient> internal)
       override;
   void GetCursorLocationMemory(const GetCursorLocationMemoryCallback& callback)
       override;
   void PerformDragDrop(uint32_t change_id,
                        uint32_t source_window_id,
                        int32_t drag_pointer,
                        mojo::Map<mojo::String, mojo::Array<uint8_t>> drag_data,
                        uint32_t drag_operation) override;
+  void CancelDragDrop(uint32_t window_id) override;
   void PerformWindowMove(uint32_t change_id,
                          uint32_t window_id,
                          mojom::MoveLoopSource source,
                          const gfx::Point& cursor_location) override;
   void CancelWindowMove(uint32_t window_id) override;
 
   bool got_change_;
   uint32_t change_id_;
   std::set<uint32_t> acked_events_;
   uint32_t window_id_;
 
   DISALLOW_COPY_AND_ASSIGN(TestWindowTree);
 };
 
 }  // namespace ui
 
 #endif  // SERVICES_UI_PUBLIC_CPP_TESTS_TEST_WINDOW_TREE_H_