Finishes the render operation of the trigger Button.
@private
function() {
        var me = this,
            menuTrigger = me.menuTrigger,
            names = me.layout.names;

        // The rendering flag is set when getRenderTree is called which we do when returning markup string for the owning layout's "suffix"
        if (menuTrigger.rendering) {
            menuTrigger.finishRender();
            me.triggerTotalWidth = menuTrigger[names.getWidth]() + menuTrigger.el.getMargin(names.parallelMargins);
        }
    }