[Gallery] Add reload feature

ui/file_manager/gallery/js/background.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.
 
 /**
  * Configuration of the Gallery window.
  * @const
  * @type {Object}
  */
 var windowCreateOptions = {
   id: 'gallery',
   innerBounds: {
     minWidth: 820,
     minHeight: 554
   },
   frame: 'none'
 };
 
 /**
  * Backgound object. This is necessary for AppWindowWrapper.
  * @type {!BackgroundBase}
  */
 var background = new BackgroundBase();
 
 
+/**
+ * Wrapper of gallery window.
+ * @type {SingletonAppWindowWrapper}
+ */
+var gallery = new SingletonAppWindowWrapper('gallery.html',
+    windowCreateOptions);
+
 // Initializes the strings. This needs for the volume manager.
 var loadTimeDataPromise = new Promise(function(fulfill, reject) {
   chrome.fileManagerPrivate.getStrings(function(stringData) {
     loadTimeData.data = stringData;
     fulfill(true);
   });
 });
 
 // Initializes the volume manager. This needs for isolated entries.
 var volumeManagerPromise = new Promise(function(fulfill, reject) {
@@ skipping 33 matching lines @@
     chrome.fileManagerPrivate.resolveIsolatedEntries(
         isolatedEntries,
         function(externalEntries) {
           var urls = util.entriesToURLs(externalEntries);
           openGalleryWindow(urls, false);
         });
   });
 }
 
 /**
- * Returns a function to generate an ID for window.
- * @type {function():string} Function which returns an unique id.
- */
-var generateWindowId = (function() {
-  var seq = 0;
-  return function() {
-    return 'GALLERY_' + seq++;
-  };
-})();
-
-/**
  * Opens gallery window.
  * @param {!Array.<string>} urls List of URL to show.
  * @param {boolean} reopen True if reopen, false otherwise.
  * @return {!Promise} Promise to be fulfilled on success, or rejected on error.
  */
 function openGalleryWindow(urls, reopen) {
   return new Promise(function(fulfill, reject) {
     util.URLsToEntries(urls).then(function(result) {
       fulfill(util.entriesToURLs(result.entries));
     }).catch(reject);
   }).then(function(urls) {
     if (urls.length === 0)
       return Promise.reject('No file to open.');
 
-    var windowId = generateWindowId();
-
     // Opens a window.
     return new Promise(function(fulfill, reject) {
-      var gallery = new AppWindowWrapper('gallery.html',
-          windowId,
-          windowCreateOptions);
-
       gallery.launch(
           {urls: urls},
           reopen,
           fulfill.bind(null, gallery));
     }).then(function(gallery) {
       var galleryDocument = gallery.rawAppWindow.contentWindow.document;
       if (galleryDocument.readyState == 'complete')
         return gallery;
 
       return new Promise(function(fulfill, reject) {
@@ skipping 22 matching lines @@
   chrome.runtime.onMessageExternal.addListener(function(message) {
     if (message.name !== 'testResourceLoaded')
       return;
     var script = document.createElement('script');
     script.src =
         'chrome-extension://' + window.testExtensionId +
         '/gallery/test_loader.js';
     document.documentElement.appendChild(script);
   });
 }