[Impl nit] IDL string fields related to size declarations should be DOMString rather than USVString

[gtanzer]

The following string fields related to size declarations in the joinAdInterestGroup API surface should be DOMStrings rather than USVStrings, because there is no specific reason for them to be USVStrings (they will not appear in a UI).

sizeGroup in AuctionAd
https://source.chromium.org/chromium/chromium/src/+/main:third_party/blink/renderer/modules/ad_auction/auction_ad.idl

width and height in AuctionAdInterestGroupSize
https://source.chromium.org/chromium/chromium/src/+/main:third_party/blink/renderer/modules/ad_auction/auction_ad_interest_group.idl;l=15

[morlovich]

I believe that would be a mistake. Note that we have no good way of sending DOMString fields to devtools, and we would like to send accurate information to devtools about interest groups people join.

[gtanzer]

I believe that would be a mistake. Note that we have no good way of sending DOMString fields to devtools, and we would like to send accurate information to devtools about interest groups people join.

@domfarolino @JensenPaul

[domfarolino]

Hmm, I have to imagine there are plenty of APIs and web platform features that allow DevTools introspection, but that use DOMStrings under the hood. What do those APIs do? Or can you point to the mechanism that only allows USVStrings to be passed to developer tools?

[morlovich]

We are sending a JSON object to devtools to represent complex stuff like this. Which means if it's got invalid utf-8, we check-fail.

[MattMenke2]

Also worth noting that interest groups can be updated by a URL, that's specced to contain a JSON response body. Seems like it would be a bit awkward if you could set invalid utf-8 values via JS, but not via the update API.

[domfarolino]

Regarding this issue, the last I remember was discussing this with @JensenPaul and resolving to ask around in the Chromium community about the base::Value implementation's requirements for USVString-like semantics, and if there is a way or need for us to get around that. Has discussion of that kind taken place yet?