Backed out 8 changesets (bug 914437, bug 886999, bug 890997, bug 923114, bug 923133) for suspicion of causing frequent OSX mochitest-2 timeouts on a CLOSED TREE.

Backed out changeset e934fda24887 (bug 890997)
Backed out changeset 058c2432bff5 (bug 886999)
Backed out changeset 34d9056bf553 (bug 886999)
Backed out changeset 3f053c13cf4e (bug 914437)
Backed out changeset 1f436fd67cdb (bug 886999)
Backed out changeset 7c914b3e8d27 (bug 923133)
Backed out changeset e6fdf5fd28c5 (bug 923114)
Backed out changeset b0700255080c (bug 914437)