We can re-use the same info for each level of the texture. Also use
fixed sized arrays for the subresource data structure.

Bug: chromium:867089
Change-Id: Ie43886f708d1141fb80d30a78cabdd37dfbf6f94
Reviewed-on: https://chromium-review.googlesource.com/1149082Reviewed-by: Geoff Lang <geofflang@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>