controlRdc_(pts) {
    this.type_ = shaka.cea.Cea608DataChannel.CaptionType.PAINTON;
    // Point to displayed memory.
    this.curBuf_ = this.displayedMemory_;

    // No scroll window now.
    this.curBuf_.setScrollSize(0);

    // The next paint-on caption needs this time as the start time.
    this.prevEndTime_ = pts;
  }
Handles RDC - Resume Direct Captions. Initiates Paint-On captioning mode.
RDC does not affect current display, so nothing needs to be forced out yet.
@param {number} pts in seconds
@private