The patch consists of three different changes:

1) CancelSilentlyMarker is changed from a job to an atomic flag.
   Before this change, the job used to be cancelled before the
   actual flag was reset. It caused too many unnecessary updates
   to happen.

2) KisFilterStrokeStrategy now provides a cookie to show whether
   the procesing has finished or not.

3) This cookie is used in a new mode in KisSignalCompressor. This
   mode works as the normal FIRST_ACTIVE mode, with one exception:
   it has "the second" shorter timer that checks if the queue is
   already idle. If it is idle, then the signal will be passed
   before the normal deadline. This mode is activated by calling
   the second override of setDelay() that accepts isIdle callback
   for the state of the queue.