When browsing https://sr.wikipedia.org/ for example (after dismissing the local site notice), on every subsequent page visit the site notice is still shown every time briefly before being hidden (bump and un-bump) this is a nuisance to the end-user.

Previously this "worked" by executing JavaScript in the top queue synchronously before the first render. The code in question (ext.dismissableSiteNotice.js) adds an inline stylesheet to the page that will inform the browser ahead of time to hide the sitenotice if the dismiss cookie is set. Then, when the browser proceeded to parse and render the page, the site notice was display-none from the first render directly.

We need to figure out a different way to do this, and it has to work for anonymous users as well.