disposeMarker_(workspaceId) {
    if (!this.getMarkerManager_()) {
      throw Error('Cannot dispose of a Marker without Blockly MarkerManager.');
    }
    try {
      this.getMarkerManager_().unregisterMarker(workspaceId);
    } catch {}
  }
Unregister the Marker from Blockly MarkerManager and dispose the marker.
@param {!String} workspaceId The workspaceId of the user whose marker is
getting disposed.
@throws Throws an error if there is no Blockly MarkerManager.
@private