WebGL2 shaders have added restriction to improve portability for some
OpenGL compilers that do not support arbitrary ternary and sequence
operators. It disallows these operators for arrays, structs containing
arrays and the void type.

BUG=612066

Change-Id: Id11042051bce25a91e57deaa9591d4d813fed7aa
Reviewed-on: https://chromium-review.googlesource.com/359949Reviewed-by: Olli Etuaho <oetuaho@nvidia.com>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Corentin Wallez <cwallez@chromium.org>