With https://bugzilla.mozilla.org/show_bug.cgi?id=1023609 mozilla has removed let expression/block
support. This prevents conkeror from starting up with current gecko-dev head. Attached patch converts the
instances I found to normal let statements.

Thank you dunio for this patch!

Do you know if applying this patch (and using the new let syntax) would break Conkeror on older versions
of gecko that don't use the new let syntax?

Is it the case that there's no way to support both the old and new versions of gecko without removing all
let expressions?

Sorry about misspelling donio.

Issue that removes let blocks:
https://bugzilla.mozilla.org/show_bug.cgi?id=1167029

Description of differences between old and new let:
https://blog.mozilla.org/addons/2015/10/14/breaking-changes-let-const-firefox-nightly-44/

Looks like const will need to be updated as well.

Perhaps rewriting the let uses to not use let would be best.

Fixed in commit 631644f5c4a6bc544312603eab8ae4deed0f125e. Thanks for the analysis and patch!

Please open a new issue in case this patch causes any regressions.