Bug 967457 - Fix a benign TSan data race in BytecodeTypes. r=bhackett

--HG--
extra : rebase_source : 5a5a4b1641611ee92aa3e948b3cb0805b9ca70fb
Bug 967474 - Fix TypeScript initialization to not race with compilation threads. r=bhackett

--HG--
extra : rebase_source : 28b5cc109a2656a3ea1c21dc398da08db90926c8