code: function drawRadialBorder(radius, width, context, start, end) {
      context.beginPath();
      //noinspection JSUnresolvedFunction
      context.arc(0, 0, abs(radius), 0, PI * 2, true);
      context.lineWidth = width;
      context.strokeStyle = end ?
          drawings.linearGradient(context, start, end, radius) :
          start;
      context.stroke();
      context.closePath();
  }
docs: /* istanbul ignore next: private, not testable 
  Draws gradient-filled circle on a canvas
  
  @access private
  @param {number} radius
  @param {number} width
  @param {Canvas2DContext} context
  @param {string} start gradient start color
  @param {string} end gradient end color