controlEoc_(pts) {
    let parsedClosedCaption = null;
    if (this.type_ !== shaka.cea.Cea608DataChannel.CaptionType.TEXT) {
      parsedClosedCaption =
        this.displayedMemory_.forceEmit(this.prevEndTime_, pts);
    }
    // Swap memories
    const buf = this.nonDisplayedMemory_;
    this.nonDisplayedMemory_ = this.displayedMemory_;  // Swap buffers
    this.displayedMemory_ = buf;

    // Enter Pop-On mode.
    this.controlRcl_();

    // The caption ended, and so the previous end time should be updated.
    this.prevEndTime_ = pts;
    return parsedClosedCaption;
  }
Handles EOC - End Of Caption (flip mem)
This forces Pop-On mode, and swaps the displayed and nondisplayed memories.
@private
@param {number} pts
@return {?shaka.extern.ICaptionDecoder.ClosedCaption}