getPlaybackRate() {
    if (!this.video_) {
      return 0;
    }
    return this.playRateController_ ?
           this.playRateController_.getRealRate() :
           1;
  }
Get the playback rate of what is playing right now. If we are using trick
play, this will return the trick play rate.
If no content is playing, this will return 0.
If content is buffering, this will return the expected playback rate once
the video starts playing.

<p>
If the player has not loaded content, this will return a playback rate of
0.

@return {number}
@export