Add attestations requirement for reportEvent and automatic beacons.

Fenced_Frames_Ads_Reporting.md

@@ -47,7 +47,7 @@ The following new APIs will be added for achieving this.
 
 ## reportEvent
 
-Fenced frames can invoke the `reportEvent` API to tell the browser to send a beacon with event data to a URL registered by the worklet in `registerAdBeacon` (see below). Depending on the declared `destination`, the beacon is sent to either the buyer's or the seller's registered URL. Examples of such events are mouse hovers, clicks (which may or may not lead to navigation e.g. video player control element clicks), etc.
+Fenced frames can invoke the `reportEvent` API to tell the browser to send a beacon with event data to a URL registered by the worklet in `registerAdBeacon` (see below). The registered destination is required to be attested for Protected Audience API, otherwise the beacon will not be sent. Please see [the Privacy Sandbox enrollment attestation model](https://github.com/privacysandbox/attestation#the-privacy-sandbox-enrollment-attestation-model). Depending on the declared `destination`, the beacon is sent to either the buyer's or the seller's registered URL. Examples of such events are mouse hovers, clicks (which may or may not lead to navigation e.g. video player control element clicks), etc.
 
 This API is available from same-origin frames within the initial rendered ad document and across subsequent same-origin navigations, but it's no longer available after cross-origin navigations or in cross-origin subframes. (For this API, for chains of redirects, the requestor is considered same-origin with the target only if it is same-origin with all redirect URLs in the chain.) This way, the ad may redirect itself without losing access to reporting, but other sites can't send spurious reports.
 
@@ -109,7 +109,7 @@ Note `window.fence` here is a new namespace for APIs that are only available fro
 
 ## registerAdBeacon
 
-A similar API was initially discussed here: https://github.com/WICG/turtledove/issues/99 for reporting clicks. The idea is that the buyer and seller side worklets are able to register a URL with the browser in their reportWin and reportResult APIs. A beacon will be sent to the registered URL when events are reported by the fenced frame via reportEvent.
+A similar API was initially discussed here: https://github.com/WICG/turtledove/issues/99 for reporting clicks. The idea is that the buyer and seller side worklets are able to register a URL with the browser in their reportWin and reportResult APIs. The registered URL's site is required to be attested for Protected Audience API. Please see [the Privacy Sandbox enrollment attestation model](https://github.com/privacysandbox/attestation#the-privacy-sandbox-enrollment-attestation-model). If the URL is attested for Protected Audience API, a beacon will be sent to the registered URL when events are reported by the fenced frame via reportEvent. Otherwise the beacon will not be sent.
 
 
 ### Parameters
@@ -127,6 +127,9 @@ registerAdBeacon({
 });
 ```
 
+In this example, the registered URL for the `click` event is 
+`"https://adtech.example.co.jp/click?buyer_event_id=123"`. The registrable domain of this URL is `"example.co.jp"`. [The Privacy Sandbox enrollment attestation model](https://github.com/privacysandbox/attestation#the-privacy-sandbox-enrollment-attestation-model) requires its corresponding site `"https://example.co.jp"` to be enrolled as defined in [site-based enrollment](https://developer.chrome.com/blog/announce-enrollment-privacy-sandbox/#site-based-enrollment). Otherwise the beacon will not be sent when there is a `click` event.
+
 ## Support for Attribution Reporting 
 ### Goals
 *   While fenced frames still have unrestricted network access and FLEDGE supports event-level reporting, the solution below takes advantage of the `registerAdBeacon`/`reportEvent` information flow to enable [registering attribution sources](https://github.com/WICG/attribution-reporting-api/blob/main/EVENT.md#registering-attribution-sources). [ARA attribution triggering](https://github.com/WICG/attribution-reporting-api/blob/main/EVENT.md#triggering-attribution) is unchanged for registered FLEDGE impressions.