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

ui/file_manager/file_manager/foreground/js/compiled_resources.gyp

Index: ui/file_manager/file_manager/foreground/js/compiled_resources.gyp
diff --git a/ui/file_manager/file_manager/foreground/js/compiled_resources.gyp b/ui/file_manager/file_manager/foreground/js/compiled_resources.gyp
index dd1b27a12660ccc4d64fbf0e3052a045d140b7f7..850998fb66a3712179cae558c04a73ce10e21ff5 100644
--- a/ui/file_manager/file_manager/foreground/js/compiled_resources.gyp
+++ b/ui/file_manager/file_manager/foreground/js/compiled_resources.gyp
@@ -58,7 +58,6 @@
           '../../background/js/device_handler.js',
           '../../background/js/drive_sync_handler.js',
           '../../background/js/duplicate_finder.js',
-          '../../background/js/volume_manager.js',
           '../../background/js/progress_center.js',
           '../../background/js/app_window_wrapper.js',
           '../../background/js/import_history.js',
@@ -170,11 +169,13 @@
           '<(EXTERNS_DIR)/file_manager_private.js',
           '<(EXTERNS_DIR)/metrics_private.js',
           '../../../../../third_party/analytics/externs.js',
+          '../../../externs/background_window_common.js',
           '../../../externs/chrome_echo_private.js',
           '../../../externs/chrome_webstore_widget_private.js',
           '../../../externs/chrome_test.js',
           '../../../externs/connection.js',
           '../../../externs/css_rule.js',
+          '../../../externs/entry_location.js',
           '../../../externs/es6_workaround.js',
           '../../../externs/html_menu_item_element.js',
           '../../../externs/launcher_search_provider.js',
@@ -182,6 +183,8 @@
           '../../../externs/paper_elements.js',
           '../../../externs/platform.js',
           '../../../externs/volume_info.js',
+          '../../../externs/volume_info_list.js',
+          '../../../externs/volume_manager.js',
           '../../common/js/externs.js',
         ],
       },