Support `getElementsByTagName(tag)` for DocumentFragment

[yezhizhen]

What problem are you trying to solve?

w3c/webdriver#1903
There is no reason we don't support getElementsByTagName(tag) for DocumentFragment, as it already supports querySelector, getElementById etc. Right now this causes trouble for WebDriver standard.

What solutions exist today?

Use querySelectorAll to mimic the behaviour.

How would you solve it?

No response

Anything else?

No response

[yezhizhen]

cc @xiaochengh

[annevk]

There is a reason. It's a dated API.

WebDriver has access to internal APIs or could use querySelector() so you'll have to elaborate a bit as to why that won't work.

[WebReflection]

another reason, it's a live collection, not a static one, and for short-living content (as that's what nodes in fragments do) makes (imho) very little sense to have, it would add instead confusion about suddenly empty lists on append as there are tons of people that still don't know live collections exist.