pressedTexSubImage* will result in an
  // INVALID_OPERATION error only if one of the following conditions occurs:
  // * <width> is not a multiple of four, and <width> plus <xoffset> is not
  // equal to TEXTURE_WIDTH;
  // * <height> is not a multiple of four, and <height> plus <yoffset> is
  //           not equal to TEXTURE_HEIGHT; or
  // * <xoffset> or <yoffset> is not a multiple of four.
  ctu.testTexSubImageDimensions(gl, ext, validFormats, expectedByteLength, getBlockDimensions,
    16, 16, [
     