assertIsAbove = function(a, b, opt_c) {
  'use strict';
  _validateArguments(2, arguments);
  const element = nonCommentArg(1, 2, arguments);
  const otherElement = nonCommentArg(2, 2, arguments);
  const elementRect = goog.style.getBounds(element);
  const otherElementRect = goog.style.getBounds(otherElement);

  _assert(
      commentArg(1, arguments), elementRect.top < otherElementRect.top,
      'Elements should be top to bottom.');
}
Asserts that the first element is higher than the second element.
@param {Element|string} a The first element or optionally the comment string.
@param {Element} b The second element or the first element if comment string
    is present.
@param {Element=} opt_c The second element if comment string is present.