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 632 matching lines @@
 
 // |checksum| Result checksum.
 callback ComputeChecksumCallback = void(DOMString checksum);
 
 // |extensions| List of providing extensions.
 callback GetProvidingExtensionsCallback = void(ProvidingExtension[] extensions);
 
 // |actions| List of actions.
 callback GetCustomActionsCallback = void(fileSystemProvider.Action[] actions);
 
+// |size| result size.
+callback GetDirectorySizeCallback = void(double size);
+
 interface Functions {
   // Logout the current user for navigating to the re-authentication screen for
   // the Google account.
   static void logoutUserForReauthentication();
 
   // Cancels file selection.
   static void cancelDialog();
 
   // Executes file browser task over selected files.
   // |taskId| The unique identifier of task to execute.
@@ skipping 299 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,
+                               GetDirectorySizeCallback callback);
 };
 
 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);
 };
 };