Disallow read color type conversions for norm16 formats OpenGL ES is not supposed to convert 16-bit color buffers to 8-bit pixel types or vice versa during readPixels operation. Fixed: angleproject:351644552 Change-Id: I9e51ddc82f62f958b983b5d4609f7e983a941e83 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/5686233 Commit-Queue: Alexey Knyazev <lexa.knyazev@gmail.com> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>