addRewindButtonOnControlsContainer_() {
    const hiddenRewindContainer = shaka.util.Dom.createHTMLElement('div');
    hiddenRewindContainer.classList.add(
        'shaka-hidden-rewind-container');
    this.controlsContainer_.appendChild(hiddenRewindContainer);

    /** @private {shaka.ui.HiddenRewindButton} */
    this.hiddenRewindButton_ =
        new shaka.ui.HiddenRewindButton(hiddenRewindContainer, this);
    this.elements_.push(this.hiddenRewindButton_);
  }
Add Rewind button on Controls container for moving video some seconds
behind when the video is tapped more than once, video seeks behind some
seconds for every extra tap.
@private