Bug 1633673 [wpt PR 23288] - COEP ReportingObserver integration, a=testonly

Bug 1633673 [wpt PR 23288] - COEP ReportingObserver integration, a=testonly

Automatic update from web-platform-tests
COEP ReportingObserver integration

Notify reports made by COEP to ReportingObservers registered to
documents and service workers.

Support for dedicated workers is blocked on PlzDedicatedWorker.
Support for shared workers is blocked on COEP support for shared
workers.

TESTING:
Now we have two means to test the COEP reporting functionality.
 1. Reports sent to the network.
 2. Reports observed via ReportingObserver

We need to have *some* tests with both ways, but we don't need to test
all the cases for both ways, and generally speaking ReportingObserver
is easier to use, and less flaky. Hence this CL makes
cache-storage-reporting-*.https.html use ReportingObserver. This CL
also adds reporting-subresource-corp.https.html for subresource loading
cases. I'm planning to make more COEP reporting tests use
ReportingObserver in the future.

Bug: 1052764
Change-Id: Idc670bfc957f05aae813c4a3bce7e361293fc716
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2160291
Reviewed-by: Ian Clelland <iclelland@chromium.org>
Reviewed-by: Makoto Shimazu <shimazu@chromium.org>
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Reviewed-by: Arthur Sonzogni <arthursonzogni@chromium.org>
Commit-Queue: Yutaka Hirano <yhirano@chromium.org>
Cr-Commit-Position: refs/heads/master@{#767369}

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wpt-commits: 540f25e22401fe99e72bf6da2cb1ca1748a8ca4f
wpt-pr: 23288