Created attachment 8701469 [details] screenshot of missing highlighting STR: #Open Firefox. #Visit https://support.mozilla.org/en-US/kb/search-suggestions-firefox. #Press [Ctrl] + [Shift] + [S] to open Debugger. #In Debugger, choose common-min.437e152f9a7a.js. #Scroll to the right. This works for every js file with very long lines (e.g. bugzilla is affected as well). Tested with Windows 10 and several versions of Firefox. Actual result: The syntax highlighting stops after a specific numer of characters per line. Expected result: The syntax highlighting should work everywhere.