@Override
    public void startDocument() throws SAXException {
        if (buffer) {
            events.add(new StartDocument());
        } else {
            super.startDocument();
        }
    }
Buffers a startDocument event if buffer is set to true.

@throws SAXException Not thrown.
@see stroom.pipeline.filter.AbstractXMLFilter#startDocument()
stroom-pipeline/src/test/java/stroom/pipeline/util/BufferFilter.java