Fixup commits for unused symbols

Some Tor Browser patches result in unreachable and/or unused code. This isn't a problem, in general, but when Firefox is built with -Werror, this causes a compile-time build failure. I'd like to fix these failures in our tree so we can begin pushing Try builds for our entire patchset.

This is step 0 on the larger/grander path of running the entire Firefox test suite against Tor Browser. Currently, too many unit tests fail when run on Tor Browser's patches, so this will not be useful (by itself) right now.

To be clear, I'm not sure if we should patch every unit test failure or if we should write a script that fetches the results and tells us if any failures were not expected - but this is a different topic.