docs: function enable () {
    // Sets some global options so that the trace viewer code can work.
    // It expects to be run inside of a browser, where host objects
    // (and Polymer) exist. Since they don't they need stubbing out.
    global.Polymer = function () {};
    global.Polymer.elements = {};
  
    global.HTMLUnknownElement = {};
    global.HTMLDivElement = {};
    global.document = {
      currentScript: {
        ownerDocument: {}
      },
  
      createElement: function () {
        return {
          style: {
  
          }
        };
      }
    };
  
    global.vec2 = {create: function () {}, set: function () {}};
    global.vec3 = {create: function () {}};
    global.vec4 = {create: function () {}};
    global.mat2d = {create: function () {}};
    global.mat4 = {create: function () {}};
    global.window = {
      performance: {
        now: function () {
          return Date.now();
        }
      }, webkitRequestAnimationFrame: function (cb) {
        cb();
      }, requestAnimationFrame: function (cb) {
        cb();
      }
    };
  }