Fix RGTC RG block size

From OpenGL spec 4.2

GL_COMPRESSED_RED_GREEN_RGTC2_EXT
Each 4 ร— 4 block of texels consists of 64 bits of compressed unsigned red image
data followed by 64 bits of compressed unsigned green image data.

GL_COMPRESSED_SIGNED_RED_GREEN_RGTC2_EXT
Each 4 ร— 4 block of texels consists of 64 bits of compressed signed red image data
followed by 64 bits of compressed signed green image data.

TBR=kbr@chromium.org

Bug: 1013369
Change-Id: Ie17e2224d725059e88b22851d1b60a6e9d88430f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2050615
Reviewed-by: Shrek Shao <shrekshao@google.com>
Commit-Queue: Shrek Shao <shrekshao@google.com>
Cr-Commit-Position: refs/heads/master@{#740443}
1 file changed