If you have reload_style_on_change enabled, and use dynamic appearance
styling (style-dark.css and style-light.css), then changing the
appearance doesn't update the files that are being watched for reload.
Add a method to CssReloadHelper to change the CSS file being watched,
and also provide the CSS file as a parameter to the callback so setupCss
can be called on the right file when the file watcher triggers.
BBaoVanC