Added new DriveNotificationObserver interface which all observers of Google Drive invalidations sho…

chrome/browser/google_apis/drive_notification_observer.h

+// Copyright (c) 2013 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 CHROME_BROWSER_GOOGLE_APIS_DRIVE_NOTIFICATION_OBSERVER_H_
+#define CHROME_BROWSER_GOOGLE_APIS_DRIVE_NOTIFICATION_OBSERVER_H_
+
+namespace google_apis {
+
+// Interface for classes which need to know when to check Google Drive for
+// updates.
+class DriveNotificationObserver {
+ public:
+  // Called when an observer should check Google Drive for updates.
+  virtual void CheckForUpdates() = 0;
+
+ protected:
+  virtual ~DriveNotificationObserver() {}
+};
+
+}  // namespace google_apis
+
+#endif  // CHROME_BROWSER_GOOGLE_APIS_DRIVE_NOTIFICATION_OBSERVER_H_