Shuffles and renames ash/common/wm classes

ash/common/wm_lookup.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/common/wm/wm_lookup.h"
+#include "ash/common/wm_lookup.h"
 
 namespace ash {
-namespace wm {
 
 // static
 WmLookup* WmLookup::instance_ = nullptr;
 
 // static
 void WmLookup::Set(WmLookup* lookup) {
   instance_ = lookup;
 }
 
 // static
 WmLookup* WmLookup::Get() {
   return instance_;
 }
 
-}  // namespace wm
 }  // namespace ash