Merge changes from topic "oct3"

* changes:
  BroadcastQueue: periodic internal health check.
  BroadcastQueue: mark dump methods @NeverCompile.
  More tests for BroadcastRecord.
  Relax broadcast ANR timeouts based on run_delay.
  BroadcastQueue: more debugging information.
  BroadcastQueue: add support for wait-for-barrier.
  BroadcastQueue: add support for REPLACE_PENDING.
  BroadcastQueue: add support for priority tranches.