For example, WebGL 1.0 compiler should not compile WebGL 2.0 shaders.

BUG=angle:
TEST=815

Change-Id: Iaec66fa5127426778aff6e3891e2c214048d7457
Reviewed-on: https://chromium-review.googlesource.com/226380Tested-by: Zhenyao Mo <zmo@chromium.org>
Reviewed-by: Shannon Woods <shannonwoods@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>