Gallery: Add items to GalleryDataModel before loading their metadata.

ui/file_manager/gallery/js/image_editor/image_util.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.
 
 // Namespace object for the utilities.
 var ImageUtil = {};
 
 /**
  * Performance trace.
  */
@@ skipping 527 matching lines @@
   // Loads the image. If already loaded, then forces a reload.
   var startLoad = function() {
     if (generation !== this.generation_)
       return;
 
     // Target current image.
     targetImage = this.image_;
 
     // Obtain target URL.
     if (FileType.isRaw(entry)) {
+      var timestamp =
+          item.getMetadataItem() &&
+          item.getMetadataItem().modificationTime &&
+          item.getMetadataItem().modificationTime.getTime();
       ImageLoaderClient.getInstance().load(entry.toURL(), function(result) {
         if (result.status === 'success')
           loadImage(result.data);
         else
           onError('GALLERY_IMAGE_ERROR');
       }, {
         cache: true,
-        timestamp: item.getMetadataItem().modificationTime &&
-            item.getMetadataItem().modificationTime.getTime(),
+        timestamp: timestamp,
         priority: 0  // Use highest priority to show main image.
       });
       return;
     }
 
     // Load the image directly. The query parameter is workaround for
     // crbug.com/379678, which force to update the contents of the image.
     loadImage(entry.toURL() + '?nocache=' + Date.now());
   }.bind(this);
 
@@ skipping 158 matching lines @@
 ImageUtil.getMetricName = function(name) {
   return 'PhotoEditor.' + name;
 };
 
 /**
  * Used for metrics reporting, keep in sync with the histogram description.
  * @type {Array.<string>}
  * @const
  */
 ImageUtil.FILE_TYPES = ['jpg', 'png', 'gif', 'bmp', 'webp'];