Flash.js will check whether or not the user's side has Flash supported to check whether or not to use a .gif or .swf. There's already logic written in OOUI for progress loading as a ProgressBarWidget, so ideally we should use that instead (which will also standardize part of the current UI in SocialProfile). Currently this is used for PollNY, PictureGame, QuizGame, and FanBoxes.
- OOUI docs - https://doc.wikimedia.org/oojs-ui/master/js/#!/api/OO.ui.ProgressBarWidget
- Flash.js - https://github.com/wikimedia/mediawiki-extensions-SocialProfile/blob/master/shared/flash.js
- .swf file:
- .gif files: