* When any Account is modified, MailService gets a content notification and
runs reconciliation in an AsyncTask. Reconciliation ends up calling the
AccountManager, which also runs asynchronously. The net effect is that,
especially during unit tests, where we create/destroy accounts rapidly,
these calls can "back up", ending in a situation in which the worker pool
for AsyncTask is filled, with a resulting RejectedExecutionException
* We fix this by preventing more than one request for reconciliation to
be queued at a time
* Added a unit test that thrashes the notification handler
Bug: 2937628
Change-Id: Iaf25806efb46831f31704604360df091752d9525
eb49659423