This is not enough to really fix behavior with TYPE_NULL,
but it does make things a bit better.

Bug: 10949594
Change-Id: Ia359f781cdd76a2e2c5a4c9f166025d81b931174

It was possible that fetchNextTasks() would be called by multiple
threads concurrently.
If it happens, some tasks in the task queues might be ignored.

Change-Id: Idc81c43c45e382da3850cc55b9a42c281548d2a8

Change-Id: I542db0c717c0bc05c8baa08f1e9db0a05946a99b

* commit 'cd2923a6':

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* commit 'cc670c5d':
  Import translations. DO NOT MERGE

* commit '419d5af0':
  Import translations. DO NOT MERGE
  Import translations. DO NOT MERGE
  Import translations. DO NOT MERGE
  Import translations. DO NOT MERGE
  Import translations. DO NOT MERGE
  Import translations. DO NOT MERGE
  Import translations. DO NOT MERGE
  Import translations. DO NOT MERGE
  Import translations. DO NOT MERGE
  Import translations. DO NOT MERGE

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* commit '5129f644':
  Import translations. DO NOT MERGE