Define maximum length and handling of CharacterData nodes

[annevk]

Currently we pretend that all CharacterData nodes (Text, CDATASection, ProcessingInstruction, and Comment) can have infinite length. In practice however it seems the upper limit has to be JavaScript's String's maximum length, which is 2⁵³ − 1.

Should we standardize on that and attempt to deal with the consequences for wholeText, normalize(), etc?

cc @rniwa @smaug---- @mfreed7

[smaug----]

Feels a bit overkill. I'd assume the platform has plenty of places where string length may get too large.
documentElement.textContent for example. Even though that is not modifying the DOM itself, what should happen on the caller side if there is OOM or otherwise too large string? (I think Gecko will throw some out-of-memory exception in that case)

Infra talks about something related https://infra.spec.whatwg.org/#algorithm-limits

[annevk]

I think Infra's carveout is less applicable here as String has a well-defined length. And CharacterData cannot exceed that length. So here we can in fact define reasonable behavior in all the edge cases (such as throwing or not normalizing).