In our custom implementation for handling modals dismiss signal, we use
element's `ownerDocument` field, which expectedly doesn't work well with
shadow root. Now using
[`getRootNode`](https://developer.mozilla.org/en-US/docs/Web/API/Node/getRootNode)
instead of `ownerDocument` to support shadow root case.
Without this, if RDT Frontend is hosted inside the shadow root, the
modal gets closed after any click, including on the buttons hosted by
modal:
00d42ac354/packages/react-devtools-shared/src/devtools/views/hooks.js (L228-L238)
Test plan:
- Modals work as expected for Chrome DevTools integration
- Modals work as expected at every other surfaces: browser extension,
electron wrapper for RN, inline version for web
947e7962ad