adjustRotationInternal(delta, anchor) {
    const isMoving = this.getAnimating() || this.getInteracting();
    const newRotation = this.constraints_.rotation(
      this.targetRotation_ + delta,
      isMoving,
    );
    if (anchor) {
      this.targetCenter_ = this.calculateCenterRotate(newRotation, anchor);
    }
    this.targetRotation_ += delta;
    this.applyTargetState_();
  }
@param {number} delta Relative value to add to the zoom rotation, in radians.
@param {import("./coordinate.js").Coordinate} [anchor] The rotation center.