Bug 979039 - handle errors in promises for child_process tests
Merge pull request #1483 from jsantell/979039-better-debugging-child-proc-tests

Bug 979039 - handle errors in promises for child_process tests, r=@mossop
bug 1004833 - enable e10s argument and flag

plus a new e10s test addon
Merge pull request #1484 from zombie/e10s-cfx-flag

bug 1004833 - enable e10s argument and flag, r=@gozala