Compile more Gallery targets in gyp v2.

ui/file_manager/gallery/js/compiled_resources.gyp

 # 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.
 {
   'targets': [
     {
       'target_name': 'background',
       'variables': {
         'depends': [
           '../../../../third_party/jstemplate/compiled_resources.gyp:jstemplate',
@@ skipping 118 matching lines @@
           './image_editor/image_buffer.js',
           './image_editor/image_view.js',
           './image_editor/commands.js',
           './image_editor/image_editor.js',
           './image_editor/image_transform.js',
           './image_editor/image_adjust.js',
           './image_editor/image_resize.js',
           './image_editor/filter.js',
           './image_editor/image_encoder.js',
           './image_editor/exif_encoder.js',
+          './gallery_constants.js',
           './dimmable_ui_controller.js',
           './entry_list_watcher.js',
           './error_banner.js',
           './gallery_data_model.js',
           './gallery_item.js',
           './gallery_util.js',
           './ribbon.js',
           './slide_mode.js',
           './thumbnail_mode.js',
         ],
@@ skipping 19 matching lines @@
           '../../externs/volume_manager.js',
           '../../externs/webview_tag.js',
         ],
       },
       'includes': [
         '../../compile_js.gypi',
       ],
     }
   ],
 }