Add end2end tests and unittests.

BUG=angleproject:970

Change-Id: I13fc501b24c3f11bfedc810c1ff80fcf1318877c
Reviewed-on: https://chromium-review.googlesource.com/287343Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Tested-by: Geoff Lang <geofflang@chromium.org>