[jumbo] Refactor and deduplicate some command_buffer constants

A couple of constants in the command_buffer code were duplicated
which caused symbol clashes in jumbo build experiments. This patch
tries to ensure each constant is only in the code once.

To make it possible to deduplicate kS3TCBlockWidth, ASTCBlockArray
and kASTCBlockArray, some validation code had to move from
gles2_cmd_decoder.cc to gl_utils.cc where there already were some
validators.

Bug: 864986
Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;luci.chromium.try:linux_optional_gpu_tests_rel;luci.chromium.try:mac_optional_gpu_tests_rel;luci.chromium.try:win_optional_gpu_tests_rel
Change-Id: I4ffb28630a1900a9400f29690cfb802497550077
Reviewed-on: https://chromium-review.googlesource.com/1145308
Reviewed-by: Antoine Labour <piman@chromium.org>
Commit-Queue: Daniel Bratell <bratell@opera.com>
Cr-Commit-Position: refs/heads/master@{#578244}
7 files changed