Add API to get a folder's size.

chrome/common/extensions/api/file_manager_private.idl

 // Copyright 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.
 
 // fileManagerPrivate API.
 // This is a private API used by the file browser of ChromeOS.
 [platforms=("chromeos"),
  implemented_in="chrome/browser/chromeos/extensions/file_manager/file_manager_private_api_functions.h"]
 namespace fileManagerPrivate {
 // Type of the mounted volume.
@@ skipping 951 matching lines @@
   [nocompile]
   static void getCustomActions([instanceof=Entry] object[] entries,
                                GetCustomActionsCallback callback);
 
   // Executes a custom action for a set of entries. If not possible, then an
   // error via chrome.runtime.lastError is returned.
   [nocompile]
   static void executeCustomAction([instanceof=Entry] object[] entries,
                                   DOMString actionId,
                                   SimpleCallback callback);
+
+  // Get the total size of a directory.
+  // |entry| Entry of the target directory.
+  // |callback|
+  [nocompile]
+  static void getDirectorySize([instanceof=DirectoryEntry] object entry,
+                               SimpleCallback callback);

[fukino, 2016/08/30 05:17:06]

We need to receive the directory size, so please define a callback type for this
method instead of using SimpleCallback.

[harukam, 2016/08/30 06:33:42]

Acknowledged.

 };
 
 interface Events {
   static void onMountCompleted(MountCompletedEvent event);
 
   static void onFileTransfersUpdated(FileTransferStatus event);
 
   static void onCopyProgress(long copyId, CopyProgressStatus status);
 
   static void onDirectoryChanged(FileWatchEvent event);
 
   static void onPreferencesChanged();
 
   static void onDriveConnectionStatusChanged();
 
   static void onDeviceChanged(DeviceEvent event);
 
   static void onDriveSyncError(DriveSyncErrorEvent event);
 };
 };