Assume thread t1 creates OUString s, then spawns thread t2, then t2 acquires s,
then t2 signals via a channel that does not necessarily involve memory
synchronization (e.g., writes a byte into a pipe which t1 reads), then t1
releases s and can still see a refCount of 1 instead of 2.

Change-Id: I31047a1a6cc8fccc401a87849f5c3cee3642d803