Minor GC does not handle OOM gracefully. This is fine because OOM is rare and the failure path is just a MOZ_CRASH. This does, however, make any OOM tests that use oomAfterAllocations interact poorly with GGC. It should be fine to just ignore oomAfterAllocations when doing a minor GC, since that is not the failure path that oomAfterAllocations wants to test.
We needed this mechanism in bug 914614, so I added it there, with a testcase.