Bug 260480

A custom element with `delegatesFocus: true` does not correctly delegate focus if the first child of the custom element's shadow DOM is not focusable. This is common with wrapper divs and styling. ``` <!-- Does not delegate focus correctly --> <x-button> #shadow-root <div class="style"> <button><slot></slot></button> </div> </x-button> <!-- Delegates focus correctly --> <x-button> #shadow-root <button><slot></slot></button> </x-button> ``` See https://jsbin.com/ranuvuhiri/edit?html,output and click on "Focus button" Expected: custom element button is focused Actual: button is not focused Tested in Safari 16.6 on MacOS 13.5