Backed out 15 changesets (bug 1612824, bug 1661234, bug 1619926, bug 1612380, bug 1559530, bug 1642990) for Xpc failures. CLOSED TREE

Backed out changeset 426d017d7e46 (bug 1642990)
Backed out changeset 84ab4021d403 (bug 1559530)
Backed out changeset 82a8305543e5 (bug 1559530)
Backed out changeset 38832c1185b8 (bug 1559530)
Backed out changeset f16918c10a6b (bug 1661234)
Backed out changeset 3a13258fbd51 (bug 1661234)
Backed out changeset abf8d8b24845 (bug 1612824)
Backed out changeset 7dfeb065a385 (bug 1619926)
Backed out changeset bc9d3e210fe7 (bug 1619926)
Backed out changeset 786164c461ae (bug 1619926)
Backed out changeset d89793e9d17d (bug 1619926)
Backed out changeset d665885bc912 (bug 1619926)
Backed out changeset 9260b6620943 (bug 1619926)
Backed out changeset af69a4896f2f (bug 1619926)
Backed out changeset b9cd6b7047b9 (bug 1612380)