Don't require GL_ARB_gpu_shader5 in order to support ES 3.0. ES 3.0 doesn't require non-constant sampler array indexing, and we can't require it for ES 2 without breaking WebGL for some users. BUG=671280 Change-Id: Ib04446284acc92410a90c683a3d222871de554a8 Reviewed-on: https://chromium-review.googlesource.com/416195 Commit-Queue: Corentin Wallez <cwallez@chromium.org> Reviewed-by: Kenneth Russell <kbr@chromium.org>