This bug was filed from the Socorro interface and is report bp-76e1c621-42ea-4da7-9576-98c130170531. ============================================================= There are 7 crashes in nightly 55 with buildid 20170531100318. In analyzing the backtrace, the regression may have been introduced by patch  to fix bug 1367837.  https://hg.mozilla.org/mozilla-central/rev?node=db86dd808a1abdeed8459045e055f20236b486c3
It seems unlikely that this would be caused by bug 1367837. More likely one of Botond's scrollbar dragging patches. From the backtrace it looks like maybe state->mController is nullptr in NotifyScrollbarDragRejected?
I posted reliable STR's in bug 1369074
Great, thanks! I'll dupe this over.