Add type annotations to gallery/js/gallery.js.

ui/file_manager/externs/gallery.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.
-
-/**
- * This is a type to let closure compiler recognize extended methods to Window
- * instance at gallery/js/gallery.js.
- * @constructor
- * @extends {Window}
- */
-function GalleryWindow() {}
-
-/**
- * @param {!BackgroundComponents} backgroundComponents Background components.
- */
-window.initialize = function(backgroundComponents) {};
-
-/**
- * @param {!Array.<!Entry>} entries Array of entries.
- * @param {!Array.<!Entry>} selectedEntries Array of selected entries.
- */
-window.loadEntries = function(entries, selectedEntries) {};
-
-/**
- * @typedef {function(number, number, boolean)}
- */
-ImageBuffer.DragHandler;