Change Files app's banner controller into a banners UI class.

ui/file_manager/file_manager/main.html

Index: ui/file_manager/file_manager/main.html
diff --git a/ui/file_manager/file_manager/main.html b/ui/file_manager/file_manager/main.html
index f01f69eac3077743f8421bcdf5607a26a69bd043..1d9ae427fb4ff019a53aabe0a7c80da76a329844 100644
--- a/ui/file_manager/file_manager/main.html
+++ b/ui/file_manager/file_manager/main.html
@@ -127,12 +127,12 @@
       <script src="foreground/js/spinner_controller.js"></script>
       <script src="foreground/js/task_controller.js"></script>
       <script src="foreground/js/thumbnail_loader.js"></script>
+      <script src="foreground/js/ui/banners.js"></script>
       <script src="foreground/js/ui/conflict_dialog.js"></script>
       <script src="foreground/js/ui/default_action_dialog.js"></script>
       <script src="foreground/js/ui/dialog_footer.js"></script>
       <script src="foreground/js/ui/directory_tree.js"></script>
       <script src="foreground/js/ui/drag_selector.js"></script>
-      <script src="foreground/js/ui/drive_banners.js"></script>
       <script src="foreground/js/ui/error_dialog.js"></script>
       <script src="foreground/js/ui/file_grid.js"></script>
       <script src="foreground/js/ui/file_manager_ui.js"></script>