async handleEvent(event) {
    const position = Position.fromEvent(event);
    await this.sendPositionUpdate({
      workspaceId: this.workspaceId,
      position: position,
    });
  }
Create a PositionUpdate from a Blockly event and send it to the server.
@param {!Blockly.Events.Abstract} event The event for which to create a
   PositionUpdate.
@public