Remove WmLookup.

ash/mus/bridge/wm_lookup_mus.cc

-// 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.
-
-#include "ash/mus/bridge/wm_lookup_mus.h"
-
-#include "ash/common/wm_window.h"
-#include "ash/mus/bridge/wm_shell_mus.h"
-#include "ui/views/widget/widget.h"
-
-namespace ash {
-namespace mus {
-
-WmLookupMus::WmLookupMus() {
-  WmLookup::Set(this);
-}
-
-WmLookupMus::~WmLookupMus() {
-  if (WmLookupMus::Get() == this)
-    WmLookup::Set(nullptr);
-}
-
-RootWindowController* WmLookupMus::GetRootWindowControllerWithDisplayId(
-    int64_t id) {
-  return WmShellMus::Get()->GetRootWindowControllerWithDisplayId(id);
-}
-
-WmWindow* WmLookupMus::GetWindowForWidget(views::Widget* widget) {
-  return WmWindow::Get(widget->GetNativeWindow());
-}
-
-}  // namespace mus
-}  // namespace ash