onActiveStateChanged property
      
      set
      onActiveStateChanged
      (ActiveStateHandler callback) 
      
    
    
Sets the active state callback.
This callback is invoked with true when the number of active streams
goes from 0 to 1 (the connection goes from idle to active), and with
false when the number of active streams becomes 0 (the connection goes
from active to idle).
Implementation
set onActiveStateChanged(ActiveStateHandler callback);