Rename the aura_shell namespace to ash

ash/wm/window_properties.h

 // 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.
 
 #ifndef ASH_WM_WINDOW_PROPERTIES_H_
 #define ASH_WM_WINDOW_PROPERTIES_H_
 #pragma once
 
-namespace aura_shell {
+namespace ash {
 namespace internal {
 
 // Shell-specific window property keys.
 
 // Alphabetical sort.
 
 // A property key for a value from ShadowType describing the drop shadow that
 // should be displayed under the window.  If unset, no shadow is displayed.
 extern const char kShadowTypeKey[];
 
 // Alphabetical sort.
 
 }  // namespace internal
-}  // namespace aura_shell
+}  // namespace ash
 
 #endif  // ASH_WM_WINDOW_PROPERTIES_H_