Several small build errors present on Linux cropped up due to
different warning flags and platform quirks.

BUG=angle:627

Change-Id: If8f651cacf05bb06ecb129be47b12729ccc3f69b
Reviewed-on: https://chromium-review.googlesource.com/197724Reviewed-by: Shannon Woods <shannonwoods@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Tested-by: Jamie Madill <jmadill@chromium.org>