> In what way loading a site on a portal would be different to loading it on the main window?
The difference is made crystal-clear in the draft [1]:
> Every browsing context has a portal state, which may be "none" (the default), "portal" or "orphaned"... "orphaned": top-level browsing contexts which have run activate but have not (yet) been adopted
In other words, the original google.com document will be kept active in background (in "orphaned" state) and the child document can continue to interact with it by using Javascript after "adopting" it (at which point roles reverse and google.com becomes child document itself).
In theory the specification allows child document to ignore parent and let browser close it, completing transition. It also allows to perform graceful switching between child and parent, keeping each in control as long as it remains top document.
In practice, child portals will run Javascript, written by Google, and will be subject to Google's complete discretion. The distinction between first-party and third-party scripts will be erased, effectively letting Google run analytics on third-party domain, and send results back from it's own domain via Javascript proxy.
The difference is made crystal-clear in the draft [1]:
> Every browsing context has a portal state, which may be "none" (the default), "portal" or "orphaned"... "orphaned": top-level browsing contexts which have run activate but have not (yet) been adopted
In other words, the original google.com document will be kept active in background (in "orphaned" state) and the child document can continue to interact with it by using Javascript after "adopting" it (at which point roles reverse and google.com becomes child document itself).
In theory the specification allows child document to ignore parent and let browser close it, completing transition. It also allows to perform graceful switching between child and parent, keeping each in control as long as it remains top document.
In practice, child portals will run Javascript, written by Google, and will be subject to Google's complete discretion. The distinction between first-party and third-party scripts will be erased, effectively letting Google run analytics on third-party domain, and send results back from it's own domain via Javascript proxy.
[1]: https://wicg.github.io/portals/