Bug 862351 - Don't enqueue messages sent to a different inner window. r=gwagner

--HG--
extra : rebase_source : 74bf8a9000bbb323dfad42fd7aa1ab89f7a6b0f2
Merge m-c to inbound.
Bug 833964 - Don't keep a dangling pointer to a task that is about to get deleted. r=drs