Created uber tray UI for monitoring ongoing WebDrive sync operations

ash/system/drive/drive_observer.h

+// 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_
+#pragma once
+
+#include "ash/system/tray/system_tray_delegate.h"
+
+namespace ash {
+
+class DriveObserver {
+ public:
+  virtual void OnDriveRefresh(const DriveOperationStatusList& list) = 0;
+
+ protected:
+  virtual ~DriveObserver() {}
+};
+
+}  // namespace ash
+
+#endif  // ASH_SYSTEM_DRIVE_DRIVE_OBSERVER_H_