     @worker.postMessage
       message: 'finalize'
 
+  ping: =>
+    @worker.postMessage
+      message: 'ping'
+      data: @current.data
+
   destroy: =>
     @worker.terminate()
     @instance._destroy()

  addQueue: (queue) =>
    @totalSizeQueued += item.size or 0 for item in queue
    @queue = @queue.concat queue

  nextInQueue: =>
    return if @busy

      return

    if @current.message is 'ping'
      @ping()
     return

    assert.equal @current.message, 'update'

