Bug 273330 [JFace] Add API to MessageDialog to enable clients to use SWT.SHEET
A new style constant SWT.SHEET was added recently. Without adding new API in JFace, clients who are currently using the convenience methods MessageDialog.openWarning/Error/Information/Question/Confirmation would not be able to open these dialogs as sheets.
bundles/org.eclipse.jface/src/org/eclipse/jface/dialogs/MessageDialog.java
break;
        }
        case WARNING: {
            this.image = getWarningImage();
            break;
        }
        }
        this.buttonLabels = dialogButtonLabels;
        this.defaultButtonIndex = defaultIndex;
    }
    /*
     *  (non-Javadoc)
     * @see org.eclipse.jface.dialogs.Dialog#buttonPressed(int)
     */
    protected void buttonPressed(int buttonId) {
        setReturnCode(buttonId);
        close();
    }
    /*
     *  (non-Javadoc)
     * @see org.eclipse.jface.window.Window#configureShell(org.eclipse.swt.widgets.Shell)
     */
    protected void configureShell(Shell shell) {
        super.configureShell(shell);
        if (title != null) {
			shell.setText(title);
		}
        if (titleImage != null) {
			shell.setImage(titleImage);
		}