Divide volume_manager.js into files for each classes and extract interfaces from them.

ui/file_manager/video_player/js/compiled_resources.gyp

Index: ui/file_manager/video_player/js/compiled_resources.gyp
diff --git a/ui/file_manager/video_player/js/compiled_resources.gyp b/ui/file_manager/video_player/js/compiled_resources.gyp
index 92dcaf425cdb5155be713001d3281401b9d52a6d..a28ef81ad9e3c41f1df23d984795e660b093f00d 100644
--- a/ui/file_manager/video_player/js/compiled_resources.gyp
+++ b/ui/file_manager/video_player/js/compiled_resources.gyp
@@ -24,7 +24,12 @@
           '../../file_manager/common/js/volume_manager_common.js',
           '../../file_manager/background/js/app_window_wrapper.js',
           '../../file_manager/background/js/background_base.js',
-          '../../file_manager/background/js/volume_manager.js',
+          '../../file_manager/background/js/entry_location_impl.js',
+          '../../file_manager/background/js/volume_info_impl.js',
+          '../../file_manager/background/js/volume_info_list_impl.js',
+          '../../file_manager/background/js/volume_manager_factory.js',
+          '../../file_manager/background/js/volume_manager_impl.js',
+          '../../file_manager/background/js/volume_manager_util.js',
           '../../file_manager/background/js/test_util_base.js',
           'error_util.js',
           'test_util.js',
@@ -36,9 +41,12 @@
           '<(EXTERNS_DIR)/metrics_private.js',
           '../../../../third_party/analytics/externs.js',
           '../../externs/chrome_test.js',
+          '../../externs/entry_location.js',
           '../../externs/es6_workaround.js',
           '../../externs/platform.js',
           '../../externs/volume_info.js',
+          '../../externs/volume_info_list.js',
+          '../../externs/volume_manager.js',
         ],
       },
       'includes': [
@@ -92,7 +100,6 @@
           '../../file_manager/foreground/js/mouse_inactivity_watcher.js',
           '../../file_manager/foreground/js/volume_manager_wrapper.js',
           # Referenced in volume_manager_wrapper.js.
-          '../../file_manager/background/js/volume_manager.js',
           '../../image_loader/image_loader_client.js',
           'cast/cast_extension_discoverer.js',
           'cast/cast_video_element.js',
@@ -107,13 +114,17 @@
           '<(EXTERNS_DIR)/media_player_private.js',
           '<(EXTERNS_DIR)/metrics_private.js',
           '../../../../third_party/analytics/externs.js',
+          '../../externs/background_window_common.js',
           '../../externs/chrome_test.js',
           '../../externs/chrome_cast.js',
           '../../externs/chrome_webstore_widget_private.js',
+          '../../externs/entry_location.js',
           '../../externs/es6_workaround.js',
           '../../externs/platform.js',
           '../../externs/video_player_foreground.js',
           '../../externs/volume_info.js',
+          '../../externs/volume_info_list.js',
+          '../../externs/volume_manager.js',
         ],
       },
       'includes': [