code: function updateProgressBar( element, value, maximum, rating ) {
  	var barElement, progress,
  		allClasses = [
  			"snippet-editor__progress--bad",
  			"snippet-editor__progress--ok",
  			"snippet-editor__progress--good",
  		];
  
  	element.value = value;
  	domManipulation.removeClasses( element, allClasses );
  	domManipulation.addClass( element, "snippet-editor__progress--" + rating );
  
  	if ( ! this.hasProgressSupport ) {
  		barElement = element.getElementsByClassName( "snippet-editor__progress-bar" )[ 0 ];
  		progress = ( value / maximum ) * 100;
  
  		barElement.style.width = progress + "%";
  	}
  }
docs: Updates a progress bar
  
  @private
  @this SnippetPreview
  
  @param {HTMLElement} element The progress element that's rendered.
  @param {number} value The current value.
  @param {number} maximum The maximum allowed value.
  @param {string} rating The SEO score rating for this value.
  
  @returns {void}