Merge changes Ie95789c9,I3d800491,I31f6b981,Ia3a4116b,I7edd3cf7

* changes:
  Rewrite handling of failed sessions (2/n)
  Rewrite the broadcast receiver for ACTION_CANCEL_ENABLE_ROLLBACK (1/n)
  Remove #mNewRollbacks (10/n)
  Put rollbacks into #mRollbacks (9/n)
  Add a flag to facilitate merging 2 rollback collections (8/n)