@Override
    public void show() {
        if (resizeHandlerRegistration == null) {
            resizeHandlerRegistration = Window.addResizeHandler(event -> {
                initialWindowWidth = event.getWidth();
                initialWindowHeight = event.getHeight();
            });
        }
        super.show();
    }
Creates an empty dialog box specifying its "auto-hide" property. It
should not be shown until its child widget has been added using
{@link #add(Widget)}.

@param autoHide <code>true</code> if the dialog should be automatically hidden
                when the user clicks outside of it
@param modal    <code>true</code> if keyboard and mouse events for widgets not
                contained by the dialog should be ignored
stroom-core-client-widget/src/main/java/stroom/widget/popup/client/view/ResizableDialog.java