Clean up EVENT() logging. These don't need newlines, or a severity prefix. BUG=angleproject:1660 Change-Id: I8a01c55a7e3d8915f48c2a29f43ddc0a37eb64f3 Reviewed-on: https://chromium-review.googlesource.com/443353 Reviewed-by: Yuly Novikov <ynovikov@chromium.org> Commit-Queue: Jamie Madill <jmadill@chromium.org>