Bug 153387 Database item can't be dragged and dropped onto editor field
Steps to reproduce: 1.Start up BIRT in Mac OS X; 2.File->New->Project; 3.File->New->Report Design; 4.In Data Explorer, create a New Data Source, and choose "Classic Models Inc. Sample DataBase", press "Next" and then press "finish"; 5.In Data Explorer, create a New Data Set, press "Next"; 6.In the popup window, expand the "CLASSICMODELS", select and drag a item onto the editor field at right side.
data/org.eclipse.birt.report.data.oda.jdbc.ui/src/org/eclipse/birt/report/data/oda/jdbc/ui/editors/SQLDataSetEditorPage.java
} );
		setupIdentifierQuoteStringCheckBox( selectTableGroup );
		setRootElement( );
		
		addDragSupportToTree( );
	}
		
    /*
	 * 
	 * @see org.eclipse.datatools.connectivity.oda.design.internal.ui.DataSetWizardPageCore#collectDataSetDesign(org.eclipse.datatools.connectivity.oda.design.DataSetDesign)
	 */
	protected DataSetDesign collectDataSetDesign( DataSetDesign design )
	{
		if ( design != null && doc != null )
			design.setQueryText( doc.get( ) );
		if ( !formerQueryTxt.equals( design.getQueryText( ) ) )
		{
			SQLUtility.saveDataSetDesign( design );
			formerQueryTxt = design.getQueryText( );
		}
		return design;
	}
	/**
	 * Sets Splitter Weights.
	 * if left side is too wide,set weights with default value 40,60.  
	 * @param splitter
	 */
	private void setSashFormWeights( SashForm sashForm )
	{
		int leftWidth = sashForm.getChildren( )[0].computeSize( SWT.DEFAULT,