AudioPlayer: Stop using Object.observe() and Array.observe().

ui/file_manager/audio_player/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 72 matching lines @@
           '../../file_manager/foreground/js/metadata/metadata_item.js',
           '../../file_manager/foreground/js/metadata/metadata_model.js',
           '../../file_manager/foreground/js/metadata/multi_metadata_provider.js',
           '../../file_manager/foreground/js/metadata/new_metadata_provider.js',
           '../../file_manager/foreground/js/metadata/thumbnail_model.js',
           '../../file_manager/background/js/volume_manager.js',
           '../../file_manager/foreground/js/volume_manager_wrapper.js',
           '../elements/control_panel.js',
           '../elements/track_list.js',
           '../elements/audio_player.js',
-          'audio_player_model.js',
         ],
         'externs': [
           '<(EXTERNS_DIR)/chrome_extensions.js',
           '<(EXTERNS_DIR)/chrome_send.js',
           '<(EXTERNS_DIR)/file_manager_private.js',
           '<(EXTERNS_DIR)/metrics_private.js',
           '../../../../third_party/analytics/externs.js',
           '../../externs/audio_player_foreground.js',
           '../../externs/chrome_test.js',
           '../../externs/es6_workaround.js',
           '../../externs/es7_workaround.js',
           '../../externs/platform.js',
         ],
       },
       'includes': [
         '../../compile_js.gypi',
       ],
     }
   ],
 }