mash: Migrate ash/system/user to ash/common.

ash/common/system/user/tray_user.h

Index: ash/common/system/user/tray_user.h
diff --git a/ash/system/user/tray_user.h b/ash/common/system/user/tray_user.h
similarity index 95%
rename from ash/system/user/tray_user.h
rename to ash/common/system/user/tray_user.h
index 897cb8184c36e9006bd403c1ea21543dcff49fe5..1373db336a16730d7633c08e3b7465b4378e9dbd 100644
--- a/ash/system/user/tray_user.h
+++ b/ash/common/system/user/tray_user.h
@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#ifndef ASH_SYSTEM_USER_TRAY_USER_H_
-#define ASH_SYSTEM_USER_TRAY_USER_H_
+#ifndef ASH_COMMON_SYSTEM_USER_TRAY_USER_H_
+#define ASH_COMMON_SYSTEM_USER_TRAY_USER_H_
 
 #include "ash/ash_export.h"
 #include "ash/common/session/session_types.h"
@@ -93,4 +93,4 @@ class ASH_EXPORT TrayUser : public SystemTrayItem, public UserObserver {
 
 }  // namespace ash
 
-#endif  // ASH_SYSTEM_USER_TRAY_USER_H_
+#endif  // ASH_COMMON_SYSTEM_USER_TRAY_USER_H_