Moves DragDropClient to aura/client

ui/wm/public/drag_drop_client.cc

-// Copyright (c) 2012 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.
-
-#include "ui/wm/public/drag_drop_client.h"
-
-#include "ui/aura/window.h"
-#include "ui/aura/window_property.h"
-
-DECLARE_WINDOW_PROPERTY_TYPE(aura::client::DragDropClient*)
-
-namespace aura {
-namespace client {
-
-DEFINE_LOCAL_WINDOW_PROPERTY_KEY(
-    DragDropClient*, kRootWindowDragDropClientKey, NULL);
-
-void SetDragDropClient(Window* root_window, DragDropClient* client) {
-  DCHECK_EQ(root_window->GetRootWindow(), root_window);
-  root_window->SetProperty(kRootWindowDragDropClientKey, client);
-}
-
-DragDropClient* GetDragDropClient(Window* root_window) {
-  if (root_window)
-    DCHECK_EQ(root_window->GetRootWindow(), root_window);
-  return root_window ?
-      root_window->GetProperty(kRootWindowDragDropClientKey) : NULL;
-}
-
-}  // namespace client
-}  // namespace aura