Files.app: Rename FileSystemMetadata with MetadataModel.

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 FileSystemMetadata */{},
+      /* Mock MetadataModel */{},
       /* Mock EntryListWatcher */{});
   fileSystem = new MockFileSystem('volumeId');
   item = new Gallery.Item(
       new MockEntry(fileSystem, '/test.jpg'),
       null,
       {media: {mimeType: 'image/jpeg'}},
       metadataCache,
       /* original */ true);
 }
 
@@ skipping 27 matching lines @@
     // 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);
 }