Some checks in Framebuffer related functions were still ES2 only. Made some modification to fix the checks for ES3. Change-Id: Iaef6133179ea830dd599a5d66bc9698032085569 Reviewed-on: https://swiftshader-review.googlesource.com/3690Tested-by: Alexis Hétu <sugoi@google.com> Reviewed-by: Nicolas Capens <capn@google.com>
