Compile most of file_manager/background scripts in v2.

ui/file_manager/externs/progress_center_panel.js

+// Copyright 2017 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.
+
+/**
+ * @constructor
+ * @struct
+ */
+function ProgressCenterPanel() {}
+
+/**
+ * @param {string} id
+ */
+ProgressCenterPanel.prototype.dismissErrorItem = function(id) {};
+
+/**
+ * @param {!ProgressCenterItem} item
+ */
+ProgressCenterPanel.prototype.updateItem = function(item) {};
+
+/** @type {?function(string)} */
+ProgressCenterPanel.prototype.cancelCallback;
+
+/** @type {?function(string)} */
+ProgressCenterPanel.prototype.dismissErrorItemCallback;