This single class will eventually replace the four child classes.

BUG=angle:732

Change-Id: Ie2862b4458c8b1302ff4fc5fbe0e4ded3b81894d
Reviewed-on: https://chromium-review.googlesource.com/213857Reviewed-by: Brandon Jones <bajones@chromium.org>
Reviewed-by: Shannon Woods <shannonwoods@chromium.org>
Tested-by: Jamie Madill <jmadill@chromium.org>