WebGLCompat: Add test for ANGLE_instanced_arrays
WebGLCompat: Add test for ANGLE_instanced_arrays

Also adds a test for an integer overflow in DrawArrays validation.

BUG=602737

Change-Id: I71c5bd155cf919964f46e2b0b48267253cab91eb
Reviewed-on: https://chromium-review.googlesource.com/716841
Reviewed-by: Geoff Lang <b6fc25fe0362055230985c05cbfa8adb741ccc0f@chromium.org>
Commit-Queue: Corentin Wallez <470c533e86f4f848c98c7e11fffc2d043494a401@chromium.org>

ppy/angle,ppy/angle,ppy/angle,ppy/angle