+++ This bug was initially created as a clone of Bug #1772006 +++

comm-central bustage:
https://treeherder.mozilla.org/jobs?repo=comm-central&revision=63b80b2a4306cf6cd8cc1d5efc81185e9c39c066

Just a first pass to should get it compiling again. Posted here in case anyone needs it urgently.
I still need to:

1. run through and double-check I didn't screw up any string compares (doing that now)
2. reimplement nsMsgCompose::ReplaceFileURLs() (used for signatures I think - I might leave this for now if I run out of time)

OK. I think that should do it. I've checked it over, but it covers a lot of ground so I think it could really do with more eyeballs.

I did update nsMsgCompose::ReplaceFileURLs() in the end.
I had to change it to scan forwards rather than backwards. I don't think there's any test coverage. So it compiles, but no guarantees as to actually working! It does look OK to me, but definitely needs testing (and ideally a unit test or two, but I'm calling it a day for now).

Also, I've only compiled under Linux so far - might be platform-specific code (import code?) which might need tweaking too:

try build here should show up platform-specific breakage:
https://treeherder.mozilla.org/#/jobs?repo=try-comm-central&revision=461ed30ecc3a08f4dc87dfaedd7273f3e1bcf0e4

Looks like we build on mac now...
Just updated the patch with a little fixup on the windows side. Let's see if that's enough to keep it happy...

https://treeherder.mozilla.org/#/jobs?repo=try-comm-central&revision=29543348ece6bed5966bcb56f19764889f0d0169

Just added another couple of minor windows fixups. Uploaded the new patch to phab. Internet playing up here, but I think I got a new try build going. I'll leave it there for today.

Pushed by mkmelin@iki.fi:
https://hg.mozilla.org/comm-central/rev/609f81cdf457
Fix nsString-related bustage from bug 1772006. r=mkmelin