Add the Errorprone Java Compiler

These changes let the errorprone compiler find problems when building Android.
A global flag disabled Errorprone by default.

When enabled, code problems will be shown with suggestions on how to fix them.

BUG=485599

Review URL: https://codereview.chromium.org/1136573002

Cr-Commit-Position: refs/heads/master@{#335509}
17 files changed