Summary:
My MBP just crashed again during startup. I would like to
understand why every plugin compilation appears to start
up a new electron process, but until that's understood
and hopefully fixed, it's probably best to limit the number
of processes we spawn by setting an upper bound here.
N.B. My Linux box doesn't mind this at all.
Reviewed By: jknoxville, danielbuechele
Differential Revision: D17419289
fbshipit-source-id: a11562a21a984059dc35e826eb20d869df218546
2a6462641b
