public void dispatchProgress(long progressUnits) {
    long unitsDecremented = decrementRemainingAllocationUnits(progressUnits);
    eventHandlers.dispatch(new ProgressEvent(allocation, unitsDecremented));
  }
Dispatches a {@link ProgressEvent} representing {@code progressUnits} of progress on the
managed {@link #allocation}.

@param progressUnits units of progress
jib-core/src/main/java/com/google/cloud/tools/jib/builder/ProgressEventDispatcher.java