Spec: Move k-anon updates to async finish reporting step.

[MattMenke2]

Browsers should only update k-anonymity when an ad is actually used, as a mitigation against running bogus auctions to game k-anon logic.

Note that this is also where bid counts are updated (when there's a winner) and when prevWins are updated. I'll update those after this lands.

---

Preview | Diff

[qingxinwu]

Yes, we do k-anon update after navigating to winning ad!
We also update k-anon when auction failed in implementation. Need to do that in spec as well. It's up to you to fix it in this PR, or in a separate one.

[MattMenke2]

Yes, we do k-anon update after navigating to winning ad! We also update k-anon when auction failed in implementation. Need to do that in spec as well. It's up to you to fix it in this PR, or in a separate one.

This CL only moves the code about updating the k-anon status of the actual winning IG and the winning ad. I'm not seeing any discussion (winner or not) of updating the k-anon status of a non-k-anon IG that would have won the auction if it were k-anonymous. I'm not really an expert in that space, and don't plan to add that for either the success or failure case, I'm solely working on moving things that happen on ad load start so they're correctly described as happening after ad load start.

[MattMenke2]

Yes, we do k-anon update after navigating to winning ad! We also update k-anon when auction failed in implementation. Need to do that in spec as well. It's up to you to fix it in this PR, or in a separate one.

This CL only moves the code about updating the k-anon status of the actual winning IG and the winning ad. I'm not seeing any discussion (winner or not) of updating the k-anon status of a non-k-anon IG that would have won the auction if it were k-anonymous. I'm not really an expert in that space, and don't plan to add that for either the success or failure case, I'm solely working on moving things that happen on ad load start so they're correctly described as happening after ad load start.

Actually, looks like there's a TODO about this?

TODO: Run score and rank a bid on generatedBid to find the highest scoring bid that isn’t k-anonymous. After the auction, if the highest scoring bid that isn’t k-anonymous has a higher score than the highest scoring k-anonymous bid, then call increment ad k-anonymity count on it.

That actually has to be done whether there's a winner or not. So definitely more work to be done there.

[qingxinwu]

Yes, we do k-anon update after navigating to winning ad! We also update k-anon when auction failed in implementation. Need to do that in spec as well. It's up to you to fix it in this PR, or in a separate one.

This CL only moves the code about updating the k-anon status of the actual winning IG and the winning ad. I'm not seeing any discussion (winner or not) of updating the k-anon status of a non-k-anon IG that would have won the auction if it were k-anonymous. I'm not really an expert in that space, and don't plan to add that for either the success or failure case, I'm solely working on moving things that happen on ad load start so they're correctly described as happening after ad load start.

Actually, looks like there's a TODO about this?

TODO: Run score and rank a bid on generatedBid to find the highest scoring bid that isn’t k-anonymous. After the auction, if the highest scoring bid that isn’t k-anonymous has a higher score than the highest scoring k-anonymous bid, then call increment ad k-anonymity count on it.

That actually has to be done whether there's a winner or not. So definitely more work to be done there.

Yes, more work around that. This PR LGTM!