Bug 116180 [SPM]Dataset can not be previewed in report designer on Mac
Description: Pull a dataset into the layout, preview in designer there is anothing displayed. Steps: 1, Create a sample datasource. create a dataset with sql statement "select * from CLASSICMODELS.EMPLOYEES" 2, Pull the dataset to the layout of the designer. 3, Preview, there is nothing displayed.
UI/org.eclipse.birt.report.designer.ui/src/org/eclipse/birt/report/designer/internal/ui/dnd/DesignElementDragAdapter.java
System.out.println( "DND >> Drag starts." ); 
		}
	}
	/**
	 * Validates every transfer element
	 * 
	 * @param transfer
	 *            every transfer element
	 * @return if transfer element can be dragged
	 */
	protected abstract boolean validateTransfer( Object transfer );
	/**
	 * Validates types of transfer elements.
	 * <p>
	 * Default implementation is verify all types of transfer elements are same
	 * 
	 * @param transfer
	 *            transfer elements
	 * @return type is same or not
	 */
	protected boolean validateType( Object transfer )
	{
		Object[] objects = (Object[]) transfer;
		if ( objects.length <= 0 )
		{
			return false;
		}
		
		if ( objects[0] instanceof ThemeHandle )
		{