function getElementAttribute(element, attrName) {
  // Older browsers might return empty string instead of null to follow the
  // DOM 3 Core Specification.
  return genericMethodCall(
             Methods.GET_ATTRIBUTE, element, 'getAttribute', [attrName]) ||
      null;
}
Returns a specific attribute from an element without falling prey to
things like <form><input name="getAttribute"></form>.
Equivalent to {@code element.getAttribute("foo")}.
@param {!Element} element
@param {string} attrName
@return {?string}