Rather than attempt to submit this behemoth to MozReview or Splinter, please just have a look at the commit at https://hg.mozilla.org/users/gszorc_mozilla.com/firefox/raw-rev/db0004d9a749 (warning: large file, may cause browser to hang).

https://bugzilla.mozilla.org/show_bug.cgi?id=1322769#c6

Bug 367116 - Hang loading 20MB text/plain page
Reported: 2007-01-16 05:22

https://bugzilla.mozilla.org/show_bug.cgi?id=367116

это всё что вам нужно знать о фуррифоксе