Update WebGL BPTC and RGTC validation logic

Fixing several BPTC and RGTC texture validation logic according to
recent WebGL spec and test updates:

https://github.com/KhronosGroup/WebGL/pull/3105
https://github.com/KhronosGroup/WebGL/pull/3111
https://github.com/KhronosGroup/WebGL/pull/3112

Bug: 1100834, 1102924
Change-Id: I82938a642821308a08e6f73175553f312c1c0e8c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2285179
Commit-Queue: Shrek Shao <shrekshao@google.com>
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#786536}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: b70dfeaf2a492cb8affd541be26abc0fd443bbe3
1 file changed