Bug 1004110 - Memoize PCToLineNumber lookups in SavedStacks. r=terrence
Bug 1019923 - Prevent multiple confusing error logs in case the data channels does not get established. r=jib
Bug 1021776 - Disable peerIdentity test on B2G. r=RyanVM
Bug 1026704 - Prefer FMP4 over GStreamer. r=rillian

This change has to be made because FMP4 is meant to take over GStreamer for MP4 file format. This way, FMP4 will be instantiated by default over GStreamer if both tools work (on a certain Linux platform).