Description

Closes #4844

I used ViteDevServer.resolvedUrls to grab the url for browser testing. I think this should be always available and If this is not available, then it's probably a Vite bug, so I didn't put any fallback or validation here.

On a related note, currently Vite's base config is not supported yet (as reported in #4686), but ViteDevServer.resolvedUrls will be also generated according to base config, so I think treating resolvedUrls as a single source of truth is appropriate for browser testing.
(Actually base doesn't change browser testing url since it's always root /, but I guess it would still make sense to use resolvedUrls as a way to get origin.)

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