There are a few minor differences between this and Mozilla's implementation:
(a) The type error messages were not hardcoded to the Performance class and were moved to Errors.msg or domerr.msg instead.
(b) Resist fingerprinting-pref changes were skipped.
Partially based on https://bugzilla.mozilla.org/show_bug.cgi?id=1724645
Since these are just interpreted comments, there's 0 impact on actual code.
This removes all lines that match /* vim: set(.*)tw=80: */ with S&R -- there are
a few others scattered around which will be removed manually in a second part.
