7e91fcdaf6
Patch addresses intermittent issue with the context menu item alwaysOpenSimilarFiles for the Downloads Panel by using the content type provided by MimeService, rather than relying on download instance. Not only does this ensure that content type exists, but it happens to also have the benefit of making alwaysOpenSimilarFiles available to more file types that can be supported. browser_downloads_panel_context_menu.js was modified to register mimeInfo and add more test cases for visibility with application/octet-stream. Differential Revision: https://phabricator.services.mozilla.com/D131881