This is a generic std::array sized to gl::MAX_VERTEX_ATTRIBS.

Bug: angleproject:2264
Change-Id: I788659ad25be5708dbab422ac4a16dff60abf154
Reviewed-on: https://chromium-review.googlesource.com/790750Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>