Check all code against error-prone; enforce correctness for future commits #100
Description
(Forking from #1)
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Do a one-time pass using error-prone to check for common mistakes in the Volley code base.
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Add gradle tasks to check the tree; run this as part of CI builds so PRs can be flagged when they fail these checks. There is at least one existing plugin that claims to do this which we might be able to use.