code: function getBreakpointSizes(element) {
    var breakpointString = element.getAttribute('data-breakpoints');
  
    var knownSizes = Util.map(function(s) {
      return Util.parseInteger(s);
    }, breakpointString ? breakpointString.split(',') : []);
  
    if (knownSizes.length <= 0) {
      return [0];
    } else {
      return Util.sortBy(knownSizes, function sortAscending(a, b) {
        return b - a;
      });
    }
  }
docs: Parse the breakpoints = require(the `data-breakpoints` attribute.
  @param {Element} element The source element.
  @return {Array} Sorted array of known sizes.