Sync web-platform-tests PR 20018 into mozilla-central (this bug is closed when the sync is complete).

PR: https://github.com/web-platform-tests/wpt/pull/20018
Details from upstream follow.

Alex Turner <alexmt@chromium.org> wrote:

Add Web Platform Tests for the Split Cache

We add a web platform test for the cache when it is partitioned by top-
frame origin. The test caches a resource, then attempts to load it in
a popup window. With the split cache, if the popup window is
cross-origin, we would expect that request to be a cache miss. We
compare the number of requests that hit the server to our expectations.
To enable these tests, the existing framework is slightly refactored,
including to respond to CORS preflight requests.

The virtual test suites virtual/split-http-cache and
virtual/not-split-http-cache explicitly test the cases of a split and
not-split cache, respectively. Given that the split cache is not enabled
by default, the default test expectations are those of a not-split
cache.

Bug: 981970
Change-Id: I049fdaec4aebcbdeebdd3c77d13d6ca420d1bd62
Reviewed-on: https://chromium-review.googlesource.com/1890952
WPT-Export-Revision: f289e2893f2f77701b9f06fb5f4fb5f9e413578f

GitHub CI Results

wpt.fyi PR Results Base Results

Ran 10 tests and 114 subtests

Firefox

OK : 10
PASS: 85
FAIL: 29

Chrome

OK : 10
PASS: 82
FAIL: 32

Safari

OK : 10
PASS: 58
FAIL: 56

Gecko CI Results

Ran 10 tests and 97[android-em-7.0-x86_64-debug-geckoview,android-em-7.0-x86_64-opt-geckoview], 109[linux64-asan-opt,linux64-debug,linux64-opt,linux64-qr-debug,linux64-qr-opt,windows10-64-debug,windows10-64-opt,windows10-64-qr-debug,windows10-64-qr-opt,windows7-32-debug,windows7-32-opt] subtests
OK : 8[android-em-7.0-x86_64-debug-geckoview,android-em-7.0-x86_64-opt-geckoview], 9[linux64-asan-opt,linux64-debug,linux64-opt,linux64-qr-debug,linux64-qr-opt,windows10-64-debug,windows10-64-opt,windows10-64-qr-debug,windows10-64-qr-opt,windows7-32-debug,windows7-32-opt]
PASS : 80[linux64-asan-opt,linux64-debug,linux64-opt,linux64-qr-debug,linux64-qr-opt,windows10-64-debug,windows10-64-opt,windows10-64-qr-debug,windows10-64-qr-opt,windows7-32-debug,windows7-32-opt], 69[android-em-7.0-x86_64-debug-geckoview,android-em-7.0-x86_64-opt-geckoview]
FAIL : 28[android-em-7.0-x86_64-debug-geckoview,android-em-7.0-x86_64-opt-geckoview], 29[linux64-asan-opt,linux64-debug,linux64-opt,linux64-qr-debug,linux64-qr-opt,windows10-64-debug,windows10-64-opt,windows10-64-qr-debug,windows10-64-qr-opt,windows7-32-debug,windows7-32-opt]

Tests that are disabled

/fetch/http-cache/304-update.html
/fetch/http-cache/cc-request.html: [android-em-7.0-x86_64-debug-geckoview,android-em-7.0-x86_64-opt-geckoview]

https://hg.mozilla.org/mozilla-central/rev/85b0b1f0e7d8