Bug 211703 Support muti-view on report item.
As title described.
xtab/org.eclipse.birt.report.item.crosstab.core/src/org/eclipse/birt/report/item/crosstab/core/de/internal/CrosstabReportItemTask.java
.getAggregationOnColumn( ) == null )
					|| ( axisType == ROW_AXIS_TYPE && cell
							.getAggregationOnRow( ) == null ) )
			{
				String function = CrosstabModelUtil.getAggregationFunction(
						crosstab, cell );
				if ( function != null )
					return function;
			}
		}
		return null;
	}
	/**
	 * Gets the aggregation function for the row/column grand total in the
	 * crosstab.
	 * 
	 * @param crosstab
	 * @param axisType
	 * @param measureView
	 * @param function
	 * @return
	 * @throws SemanticException
	 */
	public void setAggregationFunction( int axisType,
			MeasureViewHandle measureView, String function )
			throws SemanticException
	{
		
		if ( crosstab == null || crosstab.getGrandTotal( axisType ) == null
				|| measureView == null || crosstab != measureView.getCrosstab( ) )