PtrQueue::locking_enqueue_completed_buffer asserts _lock->owned_by_self() and then calls enqueue_complete_buffer. It used to contain a complicated unlock / with-other-lock / relock pattern, but was simplified as part of JDK-8182703.

It is called from exactly one place, in PtrQueue::handle_zero_index, a few lines after an assert of _lock->owned_by_self().

At this point, it just adds a function call and makes the code a bit harder to understand because of the confusing name. So remove it and just call enqueue_complete_buffer directly instead.