Stop foreground depending on background in gyp v2

ui/file_manager/externs/background/media_import_handler.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.
+
+// Namespace
+var importer;
+
+importer.MediaImportHandler;
+
+/**
+ * Note that this isn't an actual FileOperationManager.Task.  It currently uses
+ * the FileOperationManager (and thus *spawns* an associated
+ * FileOperationManager.CopyTask) but this is a temporary state of affairs.
+ *
+ * @constructor
+ * @struct
+ */
+importer.MediaImportHandler.ImportTask = function() {};
+
+/** @struct */
+importer.MediaImportHandler.ImportTask.prototype = {
+  /** @return {!Promise} Resolves when task
+      is complete, or cancelled, rejects on error. */
+  get whenFinished() {}
+};
+
+/**
+ * Request cancellation of this task.  An update will be sent to observers once
+ * the task is actually cancelled.
+ */
+importer.MediaImportHandler.ImportTask.prototype.requestCancel = function() {};