[SystemInfo API] Add Storage Watch API Definition.

chrome/common/extensions/api/experimental_system_info_storage.idl

 // 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.
 
 namespace experimental.systemInfo.storage {
 
   enum StorageUnitType {
     // The storage has fixed media, e.g. hard disk or SSD.
     fixed,
     // The storage is removable, e.g. USB flash drive.
@@ skipping 13 matching lines @@
     double availableCapacity;
   };
 
   dictionary StorageChangeInfo {
     // The uniue id of the storage unit already changed.
     DOMString id;
     // The new value of the available capacity.
     double availableCapacity;
   };
 
+  // A dictionary that describes the add particular storage device watch
+  // request results.
+  dictionary AddWatchResult {
+    DOMString id;
+    boolean success;
+  };
+
   callback StorageInfoCallback = void (StorageUnitInfo[] info);
 
+  callback AddWatchCallback = void (AddWatchResult info);
+
+  callback GetAllWatchCallback = void (DOMString[] storageIds);
+
   interface Functions {
     // Get the storage information from the system. The argument passed to the
     // callback is an array of StorageUnitInfo objects.
     static void get(StorageInfoCallback callback);
+
+    // Monitor a particular storage device available change capacity.
+    static void addWatch(DOMString id, AddWatchCallback callback);
+
+    // Remove the monitor of a particular device.
+    static void removeWatch(DOMString id);
+
+    // Get all the watched storage devices.
+    static void getAllWatch(GetAllWatchCallback callback);
+
+    // Remove all the storage devices monitors.
+    static void removeAllWatch();
   };
 
   interface Events {
     // Fired when the storage device available capacity is changed.
     // |info|: The changed information for the specified storage unit.
     static void onAvailableCapacityChanged(StorageChangeInfo info);
 
     // Fired when a new removable storage is attached to the system.
     static void onAttached(StorageUnitInfo info);
 
     // Fired when a removable storage is detached from the system.
     static void onDetached(DOMString id);
   };
  
 };