@children Only Working in Chrome

Using `@children` in a custom element is only working in Chrome. Adding `@useShadowDOM` to the custom element got it working in FireFox but it does not work in Edge. My elements have slots and two types of custom elements can be nested within each other forming a multi-level menu.

@fkleuver This is a carry over from our discussion in the vNext space.

Start by reproducing the reported @children behavior in custom elements containing slots and nested menu elements across Chrome, Firefox, and Edge. Compare the result with and without @useShadowDOM; done means @children works consistently across the reported browsers, including multi-level nesting.

Written by the indexing model from the issue text.