enterVR(display, canvas) {
    this.presentedSource = canvas;
    return display.requestPresent([{
      source: canvas,
    }])
      .then(
        ()=> {},
        // this could fail if:
        // 1. Display `canPresent` is false
        // 2. Canvas is invalid
        // 3. not executed via user interaction
        ()=> this.__setState(State.ERROR_REQUEST_TO_PRESENT_REJECTED)
      );
  }
Enter presentation mode with your set VR display
@param {VRDisplay} display the display to request present on
@param {HTMLCanvasElement} canvas
@return {Promise.<TResult>}