Also, the font blacklist is updated (fixing Apple and Medium) along with new support for blocking ATSUI-incompatible data:font/* URLs, and there is a speculative fix for the long-running issue of making changing the default search engine stick (this is difficult for me to test because none of my systems seem to be affected). The guts for repairing geolocation are in this version too but I'm still dithering over the service; most likely we will use the Mozilla Location Service though I'm open to other suggestions. Remember that the only sensor data Power Macs can provide for geolocation out of the box is the WiFi SSIDs they see (but this is perfectly sufficient for MLS). This should be finalized by the time 45.9 goes to release.
Only one site has been reported as incompatible with our plan to shut down SHA-1 certificate support with FPR1. As mentioned, it would take a major site failure for me to call this plan off, but I'd still like as much testing as possible beforehand. If you haven't done it already, please go into about:config and switch security.pki.sha1_enforcement_level to 1, and report any sites that fail. This approach of complete decommissioning is essentially the same policy Google Chrome will be taking, and soon no major browser will accept SHA-1 certificates as trusted for TLS, so it's not like we're going out on a limb here. Please note that reversing this change will not be a supported configuration because (the security implications notwithstanding) it may be un-possible to allow doing so after the new NSS library is eventually transplanted in.
Once 45.9 comes out, we will switch to our own Github repository and the source code will be uploaded and maintained from there (no more changeset overlays!). However, pull requests won't be accepted unless they're tied to an issue already accepted on the worklist, and we will still enforce the policy that non-contributor bug reports need to be triaged through Tenderapp first. Watch for the repo's magical population shortly after 45.9's final release on April 18.
Unfortunately, I don't think there will be a Tenfourbird FPR1: it appears that our anonymous colleague in the Land of the Rising Sun has not made any builds since 38.9, and that is a real shame. :(