Re: [csswg-drafts] [css-view-transitions-2] Allow synchronous snapshots (#9400)

Sandbox example with `use-view-transition`: https://codesandbox.io/s/upbeat-worker-y47h74?file=/src/App.js. This simulates a heavy page transition.

Run https://y47h74.csb.app/ with 6x CPU throttling enabled to see how this feels.

You can change `startViewTransition` to `document.startViewTransition` to see slightly different blocking behaviour but with either you can see we have an unresponsive page for the majority of this time.

What I'm looking for is to be able to move the bit where we freeze the page as close to the bit where we update the DOM as possible. 

In this performance screenshot the red box is how much time visual updates and interactions are blocked and the green box is how much time that could be with some kind of synchronous `document.snapshotTransition()`

<img width="1262" alt="Screenshot 2023-09-26 at 14 41 19" src="https://github.com/w3c/csswg-drafts/assets/7850794/25375971-beb7-444d-98f1-ea9675c59f80">


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Received on Tuesday, 26 September 2023 12:45:02 UTC