Was firing GL_DEBUG_TYPE_ERROR LogGLDebugMessage() on standalone Linux.

According to OpenGL ES 3.0.4 page 289:
The number of bits that represent a 4x4 texel block is 64 bits
if internalformat is given by COMPRESSED_RGB8_ETC2.

16x16 pixels are 16 blocks, giving 128 bytes.

BUG=angleproject:1826

Change-Id: I367e5a1369e1da2906c2ffc5ca5d703b62baf578
Reviewed-on: https://chromium-review.googlesource.com/436824Reviewed-by: Yuly Novikov <ynovikov@chromium.org>
Commit-Queue: Yuly Novikov <ynovikov@chromium.org>