:(
<rdar://problem/17917949>
Actually, sometimes the timeline does resume, but it treats the paused time as 100% CPU on the paused call frame or something. Ideally, it would not count paused time against execution duration. For replay, we could drop a breakpoint marker on the timeline, and replay back to it. But that's a separate bug.
*** This bug has been marked as a duplicate of bug 136351 ***