Backed out 2 changesets (bug 893362) for check-sync-dir bustage.

Backed out changeset cb79166bb8fa (bug 893362)
Backed out changeset 9db461b687fd (bug 893362)
Bug 887826 - Disable multi-threaded profiling on b2g to reduce memory usage. r=jseward

--HG--
extra : rebase_source : c3403864cd772414ddbf5bbda30e65322832e085
Bug 875289 - Remove .done() and allow undefined to be passed to .then() and .catch(), r=mounir, sr=bz