[Bug]: Content in dialog element cannot be masked

### Version

1.42.1

### Steps to reproduce

1. Clone https://github.com/raythurnevoid/pw-dialog-bug/tree/main
2. Run `npm i && npx playwright test`
3. Cehck the snapshot under `tests\example.spec.ts-snapshots`

### Expected behavior

The content in the dialog should be masked

### Actual behavior

The content in the dialog is not masked

### Additional context

I'm running the tests only in chromium

### Environment

```shell
System:
OS: Windows 11 10.0.22631
CPU: (16) x64 AMD Ryzen 9 4900H with Radeon Graphics
Memory: 17.27 GB / 31.42 GB
Binaries:
Node: 21.6.0 - C:\Program Files\nodejs\node.EXE
npm: 10.4.0 - C:\Program Files\nodejs\npm.CMD
IDEs:
VSCode: 1.87.1 - C:\Users\rt0\AppData\Local\Programs\Microsoft VS Code\bin\code.CMD
npmPackages:
@playwright/test: ^1.42.1 => 1.42.1
playwright: ^1.42.1 => 1.42.1
```

Clone the linked reproduction, install dependencies with npm i, and run npx playwright test; inspect tests/example.spec.ts and its snapshot under tests/example.spec.ts-snapshots. Done means the Chromium snapshot shows the dialog content masked, matching the expected behavior.

Written by the indexing model from the issue text.