Bug 121287 Post BIRT M3 build: Edit Group Dialog does not present expression builder for Group On
In Edit Group dialog, there is no expression builder for the Group On field. In order to support multi-pass aggregation, the expression builder is needed to specify an expression to group on.
UI/org.eclipse.birt.report.designer.ui/src/org/eclipse/birt/report/designer/ui/dialogs/GroupDialog.java
int index = keyChooser.getSelectionIndex( );
			String oldKey = inputGroup.getKeyExpr( );
			String newKey = null;
			if ( index != -1 )
			{
				newKey = DEUtil.getExpression( columnList.get( index ) );
			}
			inputGroup.setKeyExpr( newKey );
			if ( newKey != null && !newKey.equals( oldKey ) )
			{
				SlotHandle slotHandle = null;
				if ( inputGroup instanceof ListGroupHandle )
				{
					slotHandle = inputGroup.getHeader( );
				}
				else if ( inputGroup instanceof TableGroupHandle )
				{
					if ( inputGroup.getHeader( ).getCount( ) != 0 )
					{
						RowHandle rowHandle = ( (RowHandle) inputGroup.getHeader( )
								.get( 0 ) );
						CellHandle cellHandle = (CellHandle) rowHandle.getCells( )
								.get( 0 );
						slotHandle = cellHandle.getContent( );
					}
				}
				if ( slotHandle != null )
				{
					DesignElementHandle dataItemHandle = InsertInLayoutUtil.performInsert( columnList.get( index ),
							slotHandle,