Investigate external app handler patch for 84
From !81 (comment 2717325).
There were significant changes in https://bugzilla.mozilla.org/show_bug.cgi?id=1565574, and manual testing shows a console error when clicking of URIs of not allowed protocols like
NS_ERROR_NOT_IMPLEMENTED: Component returned failure code: 0x80004001 (NS_ERROR_NOT_IMPLEMENTED) [nsIHandlerInfo.hasDefaultHandler] 2 HandlerService.js:482 fillHandlerInfo jar:file:///home/user/utils/tor/tor-browser_en-US/Browser/omni.ja!/components/HandlerService.js:482
Testing shows the PDF case seems to be handled as intended (blocking dialog displayed).
We should investigate what is causing this error and double-check the patch is working as intended.