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
message, WARNING, new String[] { IDialogConstants.OK_LABEL }, 0); 
        
        
        
        dialog.open();
        return;
    }
    /*
     * @see org.eclipse.jface.dialogs.Dialog#createButton(org.eclipse.swt.widgets.Composite,
     *      int, java.lang.String, boolean)
     */
    protected Button createButton(Composite parent, int id, String label,
            boolean defaultButton) {
        Button button = super.createButton(parent, id, label, defaultButton);
        
        
        if (defaultButton && !customShouldTakeFocus()) {
			button.setFocus();
		}
        return button;
    }
    /**
     * Return whether or not we should apply the workaround where we take focus
     * for the default button or if that should be determined by the dialog. By
     * default only return true if the custom area is a label or CLabel that
     * cannot take focus.
     *