Rename the aura_shell namespace to ash

ash/ash_switches.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_ASH_SWITCHES_H_
 #define ASH_ASH_SWITCHES_H_
 #pragma once
 
 #include "ash/ash_export.h"
 
-namespace aura_shell {
+namespace ash {
 namespace switches {
 
 // Please keep alphabetized.
 ASH_EXPORT extern const char kAuraNoShadows[];
 ASH_EXPORT extern const char kAuraTranslucentFrames[];
 ASH_EXPORT extern const char kAuraViewsAppList[];
 ASH_EXPORT extern const char kAuraWindowMode[];
 ASH_EXPORT extern const char kAuraWindowModeCompact[];
 ASH_EXPORT extern const char kAuraWindowModeNormal[];
 ASH_EXPORT extern const char kAuraWorkspaceManager[];
 
 // Utilities for testing multi-valued switches.
 ASH_EXPORT bool IsAuraWindowModeCompact();
 
 }  // namespace switches
-}  // namespace aura_shell
+}  // namespace ash
 
 #endif  // ASH_ASH_SWITCHES_H_