docs: void onWritingThreadFinished(WebSocketFrame closeFrame)
      {
          synchronized (mThreadsLock)
          {
              mWritingThreadFinished = true;
              mClientCloseFrame = closeFrame;
  
              if (mReadingThreadFinished == false)
              {
                  // Wait for the reading thread to finish.
                  return;
              }
          }
  
          // Both the reading thread and the writing thread have finished.
          onThreadsFinished();
      }