As far as I can tell, this covers all the remaining threads which we start
using PR_CreateThread, except the ones that are created inside NSPR or NSS.
This adds a AutoProfilerRegister stack class for easy registering and
unregistering. There are a few places where we still call
profiler_register_thread() and profiler_unregister_thread() manually, either
because registration happens conditionally, or because there is a variable that
gets put on the stack before the AutoProfilerRegister (e.g. a dynamically
generated thread name). AutoProfilerRegister needs to be the first object on
the stack because it uses its own `this` pointer as the stack top address.
MozReview-Commit-ID: 3vwhS55Yzt
--HG--
extra : rebase_source : dffab11abf7d4b57fa54475fd22e71b84375cd7b
48513de60f