Revert of Move GetCursor() method from WindowDelegate to its own delegate interface CursorDelegate.

ui/wm/public/cursor_delegate.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_WM_PUBLIC_CURSOR_DELEGATE_H_
-#define UI_WM_PUBLIC_CURSOR_DELEGATE_H_
-
-#include "ui/gfx/native_widget_types.h"
-#include "ui/wm/core/wm_core_export.h"
-
-namespace aura {
-class Window;
-}
-
-namespace gfx {
-class Point;
-}
-
-namespace wm {
-
-class WM_CORE_EXPORT CursorDelegate {
- public:
-  virtual gfx::NativeCursor GetCursorForPoint(const gfx::Point& point) = 0;
-
- protected:
-  virtual ~CursorDelegate() {}
-};
-
-WM_CORE_EXPORT void SetCursorDelegate(aura::Window* window,
-                                      CursorDelegate* delegate);
-WM_CORE_EXPORT CursorDelegate* GetCursorDelegate(aura::Window* window);
-
-}  // namespace wm
-
-#endif  // UI_WM_PUBLIC_CURSOR_DELEGATE_H_