Bug 273489 [Mac] We should not nest sheets
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/internal/ide/dialogs/PathVariableDialog.java
private void createWidgets(Composite contents) {
        String nameLabelText = IDEWorkbenchMessages.PathVariableDialog_variableName;
        String valueLabelText = IDEWorkbenchMessages.PathVariableDialog_variableValue;
        
        variableNameLabel = new Label(contents, SWT.LEAD);
        variableNameLabel.setText(nameLabelText);
     
        
        variableNameField = new Text(contents, SWT.SINGLE | SWT.BORDER);
        variableNameField.setText(variableName);
        variableNameField.setLayoutData(new GridData(SWT.FILL, SWT.CENTER, true,
        		false));
        variableNameField.addModifyListener(new ModifyListener() {
            public void modifyText(ModifyEvent event) {
                variableNameModified();
            }
        });
        
        
        new Label(contents, SWT.LEAD);
        
        
        variableValueLabel = new Label(contents, SWT.LEAD);
        variableValueLabel.setText(valueLabelText);
        
        variableValueField = new Text(contents, SWT.SINGLE | SWT.BORDER);
        variableValueField.setText(variableValue);
        variableValueField.setLayoutData(new GridData(SWT.FILL, SWT.CENTER, true,
        		false));
        variableValueField.addModifyListener(new ModifyListener() {