Remove WmLookup.

ash/aura/wm_lookup_aura.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_AURA_WM_LOOKUP_AURA_H_
-#define ASH_AURA_WM_LOOKUP_AURA_H_
-
-#include "ash/common/wm_lookup.h"
-#include "base/macros.h"
-
-namespace ash {
-
-// Aura implementation of WmLookup.
-class WmLookupAura : public WmLookup {
- public:
-  WmLookupAura();
-  ~WmLookupAura() override;
-
-  // WmLookup:
-  RootWindowController* GetRootWindowControllerWithDisplayId(
-      int64_t id) override;
-  WmWindow* GetWindowForWidget(views::Widget* widget) override;
-
- private:
-  DISALLOW_COPY_AND_ASSIGN(WmLookupAura);
-};
-
-}  // namespace ash
-
-#endif  // ASH_AURA_WM_LOOKUP_AURA_H_