Add API to get a folder's size.

third_party/closure_compiler/externs/file_manager_private.js

 // Copyright 2014 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.
 
 /** @fileoverview Externs generated from namespace: fileManagerPrivate */
 
 /**
  * @typedef {{
  *   taskId: string,
  *   title: string,
@@ skipping 632 matching lines @@
 
 /**
  * Requests fetching list of actions for the specified set of entries. If not
  * possible, then returns an error via chrome.runtime.lastError.
  * @param {!Array<!Entry>} entries
  * @param {function((!Array<!EntryAction>|undefined))} callback
  */
 chrome.fileManagerPrivate.getCustomActions = function(entries, callback) {};
 
 /**
+ * Get the total size of a directory. |entry| Entry of the target directory.
+ * |callback|
+ * @param {!DirectoryEntry} entry
+ * @param {function(number)} callback
+ */
+chrome.fileManagerPrivate.getDirectorySize = function(entry, callback) {};
+
+/**
  * Executes the action on the specified set of entries. If not possible, then
  * returns an error via chrome.runtime.lastError.
  * @param {!Array<!Entry>} entries
  * @param {string} actionId
  * @param {function()} callback
  */
 chrome.fileManagerPrivate.executeCustomAction = function(
     entries, actionId, callback) {};
 
 /** @type {!ChromeEvent} */
@@ skipping 20 matching lines @@
 /** @type {!ChromeEvent} */
 chrome.fileManagerPrivate.onDriveSyncError;
 
 /** @enum {string} */
 chrome.fileManagerPrivate.Verb = {
   OPEN_WITH: 'open_with',
   ADD_TO: 'add_to',
   PACK_WITH: 'pack_with',
   SHARE_WITH: 'share_with',
 };