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
}
	/**
	 * Deletes the given view.
	 * 
	 * @param viewElement
	 *            the element
	 * @throws SemanticException
	 */
	public void dropView( DesignElementHandle viewElement )
			throws SemanticException
	{
		MultiViewsHandle multiView = getMultiViews( );
		if ( multiView == null )
			return;
		multiView.dropView( viewElement );
	}
	/**
	 * Sets the index for the view to be used. If the given element is not in
	 * the multiple view, it will be added and set as the active view.
	 * 
	 * @param viewElement
	 *            the view element
	 * 
	 * @throws SemanticException
	 *             if the given element resides in the other elements.
	 */
	public void setCurrentView( DesignElementHandle viewElement )
			throws SemanticException
	{
		if ( viewElement == null )