If it does, when the scanExternalObjectGraph call finishes and the autorelease pool is drained, we will dealloc the JSVirtualMachine which will cause us to try to take the API lock for the corresponding VM. If this happens on a GC thread other than the "main" thread, we will deadlock. The solution is to just check the VM cache, and if there is no JSVirtualMachine wrapper, return early.
Created attachment 201659 [details]
Committed r150050: <http://trac.webkit.org/changeset/150050>