mage validation on level dimensions combinations.
  // When level equals 0, width and height must be a multiple of 4.
  // When level is larger than 0, this constraint doesn't apply.

  let npotExpectation, npotMessage;
  if (contextVersion >= 2) {
    npotExpectation = gl.NO_ERROR;
    npotMessage = "valid";
  } else {
    npotExpectation = gl.INVALID_VALUE;
    npotMessage = "invalid";
  }

  ctu.testTexImageLevelDimensions(gl, ext, validFormats, expectedByteLength, getBlockDimensions,
    [
      { level