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/MessageDialogWithToggle.java
/**
     * The value of the preference when the user has asked that the answer to
     * the question always be "okay" or "yes".
     */
    public static final String ALWAYS = "always"; 
    /**
     * The value of the preference when the user has asked that the answer to
     * the question always be "no".
     */
    public static final String NEVER = "never"; 
    /**
     * The value of the preference when the user wishes to prompted for an
     * answer every time the question is to be asked.
     */
    public static final String PROMPT = "prompt"; 
    /**
     * Convenience method to open a standard error dialog.
     * 
     * @param parent
     *            the parent shell of the dialog, or <code>null</code> if none
     * @param title
     *            the dialog's title, or <code>null</code> if none
     * @param message
     *            the message