Add response status code to Resource Timing

[chromium-wpt-export-bot]

This CL introduces a responseStatus field to Performance Resource
Timing object. This field is behind a Runtime Enabled Flag.

Resource Timing PR : w3c/resource-timing#335
Fetch PR : whatwg/fetch#1468

Bug: 1343293
Change-Id: I60d1b6ba00f055481ca526a490144d88ddaf881b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3754923
Reviewed-by: Noam Rosenthal <[email protected]>
Commit-Queue: Abin Paul <[email protected]>
Reviewed-by: Yoav Weiss <[email protected]>
Reviewed-by: Takashi Toyoshima <[email protected]>
Reviewed-by: Mike West <[email protected]>
Reviewed-by: Yutaka Hirano <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1040902}

[wpt-pr-bot]

The review process for this patch is being conducted in the Chromium project.

[WeizhongX]

WPT Command: python3 ./wpt run --channel=nightly --verify --verify-no-chaos-mode --verify-repeat-loop=0 --verify-repeat-restart=10 --github-checks-text-file=/home/test/artifacts/checkrun.md --affected base_head --log-mach-level=info --log-mach=- -y --no-pause --no-restart-on-unexpected --install-fonts --no-headless --verify-log-full --binary=/home/test/build/firefox/firefox firefox

Some affected tests had inconsistent (flaky) results:

Unstable results

Test	Subtest	Results	Messages
/resource-timing/object-not-found-adds-entry.html	Verify that a 200 null-typed object emits an entry.	FAIL: 2/10, PASS: 8/10	assert_greater_than: encodedBodySize should be greater than 0 expected a number greater than 0 but got 0
/resource-timing/object-not-found-adds-entry.html	Verify that a 404 null-typed object emits an entry.	FAIL: 2/10, PASS: 8/10	assert_greater_than: encodedBodySize should be greater than 0 expected a number greater than 0 but got 0
/resource-timing/object-not-found-adds-entry.html	Verify that a 404 img-typed object emits an entry.	FAIL: 1/10, PASS: 9/10	assert_greater_than: encodedBodySize should be greater than 0 expected a number greater than 0 but got 0
/resource-timing/object-not-found-after-TAO-cross-origin-redirect.html		ERROR: 2/10, OK: 8/10
/resource-timing/object-not-found-after-TAO-cross-origin-redirect.html	There should be one entry.	FAIL: 2/10, PASS: 8/10	assert_equals: There should be one entry. expected 1 but got 0
/resource-timing/object-not-found-after-TAO-cross-origin-redirect.html	redirectStart > 0 in timing allowed cross-origin redirect.	PASS: 8/10, MISSING: 2/10
/resource-timing/object-not-found-after-TAO-cross-origin-redirect.html	redirectStart == startTime in timing allowed cross-origin redirect.	PASS: 8/10, MISSING: 2/10
/resource-timing/object-not-found-after-TAO-cross-origin-redirect.html	redirectEnd > redirectStart in timing allowed cross-origin redirect.	PASS: 8/10, MISSING: 2/10
/resource-timing/object-not-found-after-TAO-cross-origin-redirect.html	fetchStart >= redirectEnd in timing allowed cross-origin redirect.	PASS: 8/10, MISSING: 2/10

These may be pre-existing or new flakes. Please try to reproduce (see the above WPT command, though some flags may not be needed when running locally) and determine if your change introduced the flake. If you are unable to reproduce the problem, please tag @web-platform-tests/wpt-core-team in a comment for help.

[nihardamar]

bug https://bugs.chromium.org/p/chromium/issues/detail?id=1358295
@KyleJu can we admin merge this one?