code: function resizeCanvasToDisplaySize(canvas, multiplier) {
      multiplier = multiplier || 1;
      var width  = canvas.clientWidth  * multiplier | 0;
      var height = canvas.clientHeight * multiplier | 0;
      if (canvas.width !== width ||  canvas.height !== height) {
        canvas.width  = width;
        canvas.height = height;
        return true;
      }
      return false;
    }
docs: Resize a canvas to match the size its displayed.
  @param {HTMLCanvasElement} canvas The canvas to resize.
  @param {number} [multiplier] amount to multiply by.
  Pass in window.devicePixelRatio for native pixels.
  @return {boolean} true if the canvas was resized.
  @memberOf module:webgl-utils