mash: Migrate some system user files to common.

ash/common/system/user/button_from_view.h

Index: ash/common/system/user/button_from_view.h
diff --git a/ash/system/user/button_from_view.h b/ash/common/system/user/button_from_view.h
similarity index 93%
rename from ash/system/user/button_from_view.h
rename to ash/common/system/user/button_from_view.h
index fb39b505780f3b9d09063808a7946b4641e0a9c8..ba78b155de69fefd5f5caba594f7cae79cf425d6 100644
--- a/ash/system/user/button_from_view.h
+++ b/ash/common/system/user/button_from_view.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_BUTTON_FROM_VIEW_H_
-#define ASH_SYSTEM_USER_BUTTON_FROM_VIEW_H_
+#ifndef ASH_COMMON_SYSTEM_USER_BUTTON_FROM_VIEW_H_
+#define ASH_COMMON_SYSTEM_USER_BUTTON_FROM_VIEW_H_
 
 #include "base/macros.h"
 #include "ui/gfx/geometry/insets.h"
@@ -67,4 +67,4 @@ class ButtonFromView : public views::CustomButton {
 }  // namespace tray
 }  // namespace ash
 
-#endif  // ASH_SYSTEM_USER_BUTTON_FROM_VIEW_H_
+#endif  // ASH_COMMON_SYSTEM_USER_BUTTON_FROM_VIEW_H_