o Removed features:
    - Remove the code that would try to aggressively flush controller
      connections while writing to them.  This code was introduced in
      0.1.2.7-alpha, in order to keep output buffers from exceeding their
      limits.  But there is no longer a maximum output buffer size, and
      flushing data in this way caused some undesirable recursions
      in our call graph. Closes ticket 16480.