Add thumbnailMetadataItem to GalleryItem.

ui/file_manager/gallery/js/gallery_data_model_unittest.js

 // Copyright 2015 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.
 
 
 var model;
 var fileSystem;
 var item;
 
 function setUp() {
-  var metadataCache = new MockMetadataCache();
   model = new GalleryDataModel(
-      metadataCache,
       /* Mock MetadataModel */{},
       /* Mock EntryListWatcher */{});
   fileSystem = new MockFileSystem('volumeId');
   item = new Gallery.Item(
       new MockEntry(fileSystem, '/test.jpg'),
       null,
-      {media: {mimeType: 'image/jpeg'}},
-      metadataCache,
+      /* metadataItem */ {},
+      /* thumbnailMetadataItem */ {},
       /* original */ true);
 }
 
 function testSaveItemOverwrite(callback) {
   // Mocking the saveToFile method.
   item.saveToFile = function(
       volumeManager,
+      metadataModel,
       fallbackDir,
       overwrite,
       canvas,
       callback) {
     assertTrue(overwrite);
     callback(true);
   };
   model.push(item);
   reportPromise(
       model.saveItem({}, item, document.createElement('canvas'), true).
           then(function() { assertEquals(1, model.length); }),
       callback);
 }
 
 function testSaveItemNewFile(callback) {
   // Mocking the saveToFile method.
   item.saveToFile = function(
       volumeManager,
+      metadataModel,
       fallbackDir,
       overwrite,
       canvas,
       callback) {
     assertFalse(overwrite);
     // Gallery item track new file.
     this.entry_ = new MockEntry(fileSystem, '/test (1).jpg');
     callback(true);
   };
   model.push(item);
   reportPromise(
       model.saveItem({}, item, document.createElement('canvas'), false).
           then(function() { assertEquals(2, model.length); }),
       callback);
 }