Bug 177504 Engine doesn't provide SubQuery for extended item
Engine doesn't provide SubQuery for extended item, so chart can't use container's binding to execute the query. If possible, engine could provide an option for extended item to choose whether engine could create the query, so extended item won't create SubQuery by itself.
engine/org.eclipse.birt.report.engine/src/org/eclipse/birt/report/engine/presentation/LocalizedContentVisitor.java
*            output type
	 * @param output
	 *            output
	 */
	protected IContent processExtendedContent( IForeignContent content, int type,
			Object output, String imageMIMEType )
	{
		assert IForeignContent.EXTERNAL_TYPE.equals( content.getRawType( ) );
		assert output != null;
		IReportContent reportContent = getReportContent( );
		
		switch ( type )
		{
			case IReportItemPresentation.OUTPUT_NONE :
				break;
			case IReportItemPresentation.OUTPUT_AS_IMAGE :
			case IReportItemPresentation.OUTPUT_AS_IMAGE_WITH_MAP :
				
				
				Object imageMap = null;
				byte[] imageContent = new byte[0];
				Object image = output;
				if ( type == IReportItemPresentation.OUTPUT_AS_IMAGE_WITH_MAP )
				{
					
					Object[] imageWithMap = (Object[]) output;
					if ( imageWithMap.length > 0 )
					{
						image = imageWithMap[0];
					}