'Record all bytes received from the child process in the C{data}
dictionary.  Fire C{onDataReceived} if it is not L{None}.'

def childDataReceived(self, name, bytes):

    self.data[name] = (self.data.get(name, '') + bytes)
    if (self.onDataReceived is not None):
        (d, self.onDataReceived) = (self.onDataReceived, None)
        d.callback(self)
