@Override
    public TaskMonitor createTaskMonitor() {
        return new TaskMonitor() {
            @Override
            public void onStart(final Task task) {
                taskCount++;
                pager.getRefreshButton().setRefreshing(taskCount > 0);
            }

            @Override
            public void onEnd(final Task task) {
                taskCount--;

                if (taskCount < 0) {
                    GWT.log("Negative task count");
                }

                pager.getRefreshButton().setRefreshing(taskCount > 0);
            }
        };
    }
The pager used to change the range of data.
stroom-core-client-widget/src/main/java/stroom/data/grid/client/PagerViewWithHeadingImpl.java