Allow dialog centering after width/height changes

[mvysny]

I'd like to implement a "maximize" button which will set the 100vw/100vh size to the dialog. That works, however the dialog stays at its current position, which leads to parts of dialog not visible. It would be good if the "maximize" button could also call dialog.center(); to re-center the dialog, in order to show it in its entirety.

[mvysny]

The trick is to clear the styles of the dialog overlay. The following Java snippet works:

    private void center(Dialog dialog) {
        final ArrayList<String> styles = new ArrayList<>();
        if (dialog.getWidth() != null) {
            styles.add("width: " + dialog.getWidth());
        }
        if (dialog.getHeight() != null) {
            styles.add("height: " + dialog.getHeight());
        }
        dialog.getElement().executeJs("this.$.overlay.$.overlay.style = '" + String.join(";", styles) + "';");
    }