private void updateMetrics(long procTime, long documentCount) {
        metric.set(PROC_DOC_COUNT_METRIC_NAME, documentCount, metricContext);
        metric.set(PROC_TIME_METRIC_NAME, procTime, metricContext);
    }
Call the DocumentProcessor of this call.

@param processing the Processing object to use
@return the progress of the DocumentProcessor that was called
docproc/src/main/java/com/yahoo/docproc/Call.java