Remove WmLookup.

ash/common/wm_lookup.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 ASH_COMMON_WM_LOOKUP_H_
-#define ASH_COMMON_WM_LOOKUP_H_
-
-#include <stdint.h>
-
-#include "ash/ash_export.h"
-
-namespace views {
-class Widget;
-}
-
-namespace ash {
-
-class RootWindowController;
-class WmWindow;
-
-// WmLookup is used to lookup various wm types.
-class ASH_EXPORT WmLookup {
- public:
-  static void Set(WmLookup* lookup);
-  static WmLookup* Get();
-
-  // Returns the RootWindowController with the specified display id, or null if
-  // there isn't one.
-  virtual RootWindowController* GetRootWindowControllerWithDisplayId(
-      int64_t id) = 0;
-
-  // Returns the WmWindow for the specified widget.
-  virtual WmWindow* GetWindowForWidget(views::Widget* widget) = 0;
-
- protected:
-  virtual ~WmLookup() {}
-
- private:
-  static WmLookup* instance_;
-};
-
-}  // namespace ash
-
-#endif  // ASH_COMMON_WM_LOOKUP_H_