code: function WorldRenderer(params) {
    this.init_(params.hideFullscreenButton);
  
    this.sphereRenderer = new SphereRenderer(this.scene);
    this.hotspotRenderer = new HotspotRenderer(this);
    this.hotspotRenderer.on('focus', this.onHotspotFocus_.bind(this));
    this.hotspotRenderer.on('blur', this.onHotspotBlur_.bind(this));
    this.reticleRenderer = new ReticleRenderer(this.camera);
  
    // Get the VR Display as soon as we initialize.
    navigator.getVRDisplays().then(function(displays) {
      if (displays.length > 0) {
        this.vrDisplay = displays[0];
      }
    }.bind(this));
  
  }
docs: The main WebGL rendering entry point. Manages the scene, camera, VR-related
  rendering updates. Interacts with the WebVRManager.
  
  Coordinates the other renderers: SphereRenderer, HotspotRenderer,
  ReticleRenderer.
  
  Also manages the AdaptivePlayer and VideoProxy.
  
  Emits the following events:
  load: when the scene is loaded.
  error: if there is an error loading the scene.
  modechange(Boolean isVR): if the mode (eg. VR, fullscreen, etc) changes.