Bug 818789 - |mach build| can now control what is built; r=glandium

DONTBUILD (NPOTB)
Merge m-c to inbound.
Bug 835355 - Fix ContentPrefService2 to properly respond to queries for nsIContentPrefService and nsIContentPrefService2 interfaces. r=mak
Bug 835730 - Properly tear down components when the profile is being shut down. r=mak