[EventPhases] Should reads after writes throw or return stale data?

[Kaiido]

I believe returning stale data is the safest choice here.
There are a lot of setters that will also trigger a read-back (e.g. scrollLeft & friends, even methods like scrollTo()) if reading in the write phase throws, these would become unusable.

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Ps: This refers to https://github.com/MicrosoftEdge/MSEdgeExplainers/blob/main/EventPhases/explainer.md (there is no label for that proposal yet).

[slightlyoff]

Appreciate the feedback! Setters like scrollLeft are something I should break out into their own example. Will get that done.

Also created a label for this explainer.