See parent task for details.

ALTERs to run:

ALTER TABLE /*_*/campaign_events
  ADD event_track_contributions TINYINT(1) DEFAULT 0 NOT NULL;

1. Where to run those changes:
   1. x1.testwiki
   2. x1.test2wiki
   3. x1.officewiki
   4. x1.wikishared
2. When to run those changes: Whenever you can
3. If the schema change is backwards compatible: Yes (the new column has a default value and all usages are behind a feature flag that's turned off in production)
4. If the schema change has been tested already on some of the test/beta wikis: Tested locally and in beta
5. if the data should be made available on the labs replicas and/or dumps: Maybe, but we don't replicate data from x1 anyway.
6. Is this schema change blocking a feature rollout? It will, although not immediately.