getWebGLContext = function (canvas) {
  if (isInIFrame()) {
    updateCSSIfInIFrame();

    // make the canvas backing store the size it's displayed.
    canvas.width = canvas.clientWidth;
    canvas.height = canvas.clientHeight;
  }

  var gl = setupWebGL(canvas);
  return gl;
}
Gets a WebGL context.
makes its backing store the size it is displayed.