docs: function(container, progress, speed) {
  		if (typeof container === 'number') {
  			speed = progress;
  			progress = container;
  			container = false;
  		}
  		var progressbar = _findProgressbar(container);
  		if (!progressbar || progressbar.classList.contains(CLASS_PROGRESSBAR_INFINITE)) {
  			return;
  		}
  		if (progress) progress = Math.min(Math.max(progress, 0), 100);
  		progressbar.offsetHeight;
  		var span = progressbar.querySelector('span');
  		if (span) {
  			var style = span.style;
  			style.webkitTransform = 'translate3d(' + (-100 + progress) + '%,0,0)';
  			if (typeof speed !== 'undefined') {
  				style.webkitTransitionDuration = speed + 'ms';
  			} else {
  				style.webkitTransitionDuration = '';
  			}
  		}
  		return progressbar;
  	}