Re: [csswg-drafts] [css-shared-element-transitions-1] Should createDocumentTransition start the transition (#7828)

I think one of the problems with starting the transition as soon as we call createDocumentTransition is that it doesn't lend many opportunities for script to register for promise observations:

```js
async function f() {
  let t = document.createDocumentTransition(...);
  t.ready.then(() => { /* synchronize my animation with the document one */ });
}
```
Could the ready promise be resolved already by the time we say `.then`? What I have to yield for some reason between create transition and ready.then?

It feels similar to something like

```js
img.src = "...";
img.onload = () => { ... }
```
which as I understand it can cause us to miss onload, and the correct thing (`onload` before `src`) in the document transition world would not be possible


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Received on Friday, 14 October 2022 14:43:35 UTC