Column Menu pop-up mis-aligned for rightmost columns in Firefox

Column menus mis-align in firefox after the first N columns. E.g. where the cells start being hidden/paged out by angular, the alignment is off (in Firefox and not in Chrome, or Safari or even IE).

http://plnkr.co/edit/N3yKPMUBVpTgL9DVXh3f?p=preview

Go to the "1st Friend" or "2nd Friend" column and you will see that the pop-up menu when it appears is misaligned-- appearing on the column before... Any other column to the right is also off...

System details: Running on Mac 10.10, with Firefox 42.0...