Bug 122869 Drag a parameter from data explorer view into a table in library, a new parameter is created automatically.
Description:Drag a parameter from data explorer view into a table in library, a new parameter is created automatically. Steps to reproduce: 1. Add a cascading parameter and a table in a library file. 2. Drag a parameter from data explorer view into a table cell in layout editor. 3. Find that a new parameter was added in data explorer view automatically.
UI/org.eclipse.birt.report.designer.ui/src/org/eclipse/birt/report/designer/internal/ui/dialogs/ExpressionTreeSupport.java
{
				event.feedback = DND.FEEDBACK_SCROLL
						| DND.FEEDBACK_INSERT_BEFORE;
			}
			public void dragOperationChanged( DropTargetEvent event )
			{
				dragEnter( event );
			}
			public void drop( DropTargetEvent event )
			{
				if ( event.data instanceof String )
					insertText( (String) event.data );
			}
		} );
	}
	/**
	 * Disposes resources.
	 * 
	 */
	public void dispose( )
	{
		if ( dropTarget != null && !dropTarget.isDisposed( ) )
		{
			dropTarget.dispose( );
		}
	}
	/**
	 * Sets the tree model.
	 * 
	 * @param tree