Return INVALID_VALUE for online BC compression As per discussion with OpenGL ES WG, implementations are allowed to generate INVALID_VALUE when online BC compression is not supported. Bug: angleproject:6441 Change-Id: I0e282c970f1e03afbc590dc9a46b8ce38d869691 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3780923 Reviewed-by: Kenneth Russell <kbr@chromium.org> Reviewed-by: Geoff Lang <geofflang@chromium.org> Commit-Queue: Alexey Knyazev <lexa.knyazev@gmail.com>