removeWatermark() {
    if (this.animationId_) {
      cancelAnimationFrame(this.animationId_);
      this.animationId_ = null;
    }
    const ctx = this.getContext2D_();
    if (!ctx) {
      return;
    }
    ctx.clearRect(0, 0, this.canvas_.width, this.canvas_.height);
  }
Removes the current watermark from the video and stops any animations.
@export