Remove the drive status from the ash try.

ash/system/drive/drive_observer.h

Index: ash/system/drive/drive_observer.h
diff --git a/ash/system/drive/drive_observer.h b/ash/system/drive/drive_observer.h
deleted file mode 100644
index a721dd44fc73c3c09f87144760c3810c41ccd4d6..0000000000000000000000000000000000000000
--- a/ash/system/drive/drive_observer.h
+++ /dev/null
@@ -1,22 +0,0 @@
-// Copyright (c) 2012 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_SYSTEM_DRIVE_DRIVE_OBSERVER_H_
-#define ASH_SYSTEM_DRIVE_DRIVE_OBSERVER_H_
-
-#include "ash/system/tray/system_tray_delegate.h"
-
-namespace ash {
-
-class DriveObserver {
- public:
-  virtual void OnDriveJobUpdated(const DriveOperationStatus& status) = 0;
-
- protected:
-  virtual ~DriveObserver() {}
-};
-
-}  // namespace ash
-
-#endif  // ASH_SYSTEM_DRIVE_DRIVE_OBSERVER_H_