Rename the aura_shell namespace to ash

ash/wm/shadow_types.cc

 // Copyright (c) 2011 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/wm/shadow_types.h"
 
 #include "ash/wm/window_properties.h"
 #include "ui/aura/window.h"
 
-namespace aura_shell {
+namespace ash {
 namespace internal {
 
 void SetShadowType(aura::Window* window, ShadowType shadow_type) {
   window->SetIntProperty(kShadowTypeKey, shadow_type);
 }
 
 ShadowType GetShadowType(aura::Window* window) {
   return static_cast<ShadowType>(window->GetIntProperty(kShadowTypeKey));
 }
 
 }  // namespace internal
-}  // namespace aura_shell
+}  // namespace ash