This is probably in the completely wrong Product/Component, but here goes:
Google Map Maker (http://www.google.com/mapmaker) lets you edit roads, places, etc., and yet editing broke in the 20120531 nightly of Firefox, which I determined with mozregression. Here is the pushlog: http://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=65fa5cb6f79c&tochange=3aa566994890
1. Open up Google Map Maker
2. Log in (if not already)
3. Zoom in all the way on the map, near roads
4. Use the Edit menu, and then select Select a Line
5. Select a road with your mouse
6. Click one of the red road bubbles, and then click "Edit" in the white tooltip that appears
7. Click "Edit this segment"
Options open up in the sidebar, allowing you to change attributes of the segment. This happens in 20120530.
Nothing happens when you click "Edit this segment."
Local bisection points to bug 758179 as having caused this, specifically:
The first bad revision is:
user: Robert O'Callahan <firstname.lastname@example.org>
date: Wed May 30 01:13:36 2012 +1200
summary: Bug 758179. Part 1: Flush layout before calling nsFrame::HandlePress/HandleRelease. r=mats
Bug 758179 got uplifted to Aurora, we'll want to track this there.
Should have been fixed by 761572.
Yep, working for me now in the latest 20120608 respin. Thanks for the fix!
Able to see the issue on Nightly 2012-06-01.
Verified fixed on FF 15b5 on Win 7 x64, Ubuntu 12.04 and Mac OS X 10.7.4.