Bug 729098 - Ability to track and rerun failed xpcshell tests; r=gps

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extra : rebase_source : da458ded1a6574a230e127331ac4c5b24e494af2
Bug 908340 - Omit test start messages from mach xpcshell output; r=gps

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extra : rebase_source : 093f7a16df7de2b89868f0c255c3884b03cd70eb