public int getCurrentPageSize() {
        return Math.min(getPageSize(), getRowCount() - getPageStart());
    }
Get the current page size. This is usually the page size, but can be less
if the data size cannot fill the current page.

@return the size of the current page
stroom-core-client-widget/src/main/java/com/google/gwt/user/cellview/client/HasDataPresenter.java