Fix bugs related to orientation change in MessageCompose

* Save reference to LoadMessageTask and cancel it in onDestroy
* Check whether we've already processed the source message
  before calling processSourceMessage
* Fixes #2097361 (Duplicate addresses in reply/reply all)
* Fixes NPE (not in Buganizer) related to fast orientation changes
  due to duplicated background task

Change-Id: Ib8115e29c9d88db1be009df4f549f925db8a1c19
1 file changed