chore(mc): Port Bug 1478404 - remove _xpcom_categories annotations as they're dead code, r=florian (#4280)
chore(mc): Port Bug 1478404 - remove _xpcom_categories annotations as they're dead code, r=florian (#4280)


sarracini/activity-stream,mozilla/activity-stream,Mardak/activity-stream,rlr/activity-streams,mozilla/activity-streams,rlr/activity-streams,mozilla/activity-stream,Mardak/activity-stream,mozilla/activity-streams,sarracini/activity-stream,rlr/activity-streams,sarracini/activity-stream,AdamHillier/activity-stream,Mardak/activity-stream,rlr/activity-streams,AdamHillier/activity-stream,sarracini/activity-stream,mozilla/activity-stream,AdamHillier/activity-stream,AdamHillier/activity-stream,mozilla/activity-stream,Mardak/activity-stream