Turn on verbose flag for compiling file_manager.

ui/file_manager/video_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 22 matching lines @@
         'externs': [
           '<(EXTERNS_DIR)/chrome_send.js',
           '<(EXTERNS_DIR)/chrome_extensions.js',
           '<(EXTERNS_DIR)/file_manager_private.js',
           '<(EXTERNS_DIR)/metrics_private.js',
           '../../../../third_party/analytics/externs.js',
           '../../externs/chrome_test.js',
           '../../externs/es6_workaround.js',
           '../../externs/platform.js',
         ],
+        'closure_args': [
+          'warning_level=VERBOSE'
+        ]
       },
       'includes': [
         '../../../../third_party/closure_compiler/compile_js.gypi'
       ],
     },
     {
       'target_name': 'video_player',
       'variables': {
         'depends': [
           '../../../../third_party/jstemplate/compiled_resources.gyp:jstemplate',
@@ skipping 40 matching lines @@
           '<(EXTERNS_DIR)/file_manager_private.js',
           '<(EXTERNS_DIR)/media_player_private.js',
           '<(EXTERNS_DIR)/metrics_private.js',
           '../../../../third_party/analytics/externs.js',
           '../../externs/chrome_test.js',
           '../../externs/chrome_cast.js',
           '../../externs/chrome_webstore_widget_private.js',
           '../../externs/es6_workaround.js',
           '../../externs/platform.js',
           '../../externs/video_player_foreground.js',
         ],

[yawano, 2015/10/15 11:09:09]

Same with compiled_resources.gyp of audio_player.

[fukino, 2015/10/15 11:23:54]

Done.

       },
       'includes': [
         '../../../../third_party/closure_compiler/compile_js.gypi'
       ],
     }
   ],
 }