fix(wpt): implement the link stylesheet request counter

Serve the link-element stylesheet.py resource through the shared WPT stash.
Preserve consuming counter reads, per-ID state, cross-port sharing and HEAD
request behavior so link load-event tests observe real request counts.

Validate the fixture with 170 Python tests and the six upstream multiple-load
subtests in Moli and Chromium, then record the previously unlisted passing case.

moli-benchmark/moli_benchmark/wpt_cross/server.py

@@ -159,6 +159,9 @@ FETCH_REDIRECT_RESOURCE_PATHS = {
     "/fetch/api/resources/redirect-empty-location.py",
 }
 FETCH_INSPECT_HEADERS_PATH = "/fetch/api/resources/inspect-headers.py"
+LINK_STYLESHEET_COUNTER_PATH = (
+    "/html/semantics/document-metadata/the-link-element/stylesheet.py"
+)
 BENCH_TIMEOUT_MULTIPLIER_QUERY = "__moli_bench_timeout_multiplier"
 FORM_ECHO_PATH = "/html/semantics/forms/form-submission-0/form-echo.py"
 FORM_SUBMISSION_PATH = (
@@ -2933,6 +2936,30 @@ def _make_handler(
                 ],
             )
 
+        def _serve_link_stylesheet_counter(self, query: str, *, emit_body: bool) -> None:
+            params = parse_qs(query, keep_blank_values=True)
+            try:
+                count = int(fetch_stash.take(params["id"][0], path=LINK_STYLESHEET_COUNTER_PATH))
+            except (KeyError, TypeError, ValueError):
+                count = 0
+            if "count" in params:
+                self._send_bytes(
+                    "text/html", str(count).encode("ascii"),
+                    emit_body=emit_body, cache_control=None,
+                )
+                return
+            try:
+                fetch_stash.put(
+                    params["id"][0], str(count + 1), path=LINK_STYLESHEET_COUNTER_PATH,
+                )
+            except (KeyError, ValueError):
+                self.send_error(500)
+                return
+            self._send_bytes(
+                "text/css", b"body {color: red;}",
+                emit_body=emit_body, cache_control=None,
+            )
+
         def _serve_script_with_content_type(self, query: str, *, emit_body: bool) -> None:
             params = parse_qs(query, keep_blank_values=True, encoding="latin-1")
             directory = wpt_root / "html/semantics/scripting-1/the-script-element"

moli-benchmark/tests/test_wpt_cross.py

@@ -4304,6 +4304,36 @@ test(() => {}, "ok");
                                 response.read(), b"FAIL" if method == "GET" else b""
                             )
 
+    def test_fixture_server_counts_link_stylesheet_requests_and_clears_on_read(self) -> None:
+        with tempfile.TemporaryDirectory() as root:
+            root_path = Path(root)
+            (root_path / "resources").mkdir()
+            (root_path / "resources" / "testharness.js").write_text("// testharness", encoding="utf-8")
+            resource = "/html/semantics/document-metadata/the-link-element/stylesheet.py"
+            fixture = root_path / resource.lstrip("/")
+            fixture.parent.mkdir(parents=True)
+            fixture.write_text("# dynamic stylesheet resource", encoding="utf-8")
+            first = "11111111-1111-4111-8111-111111111111"
+            second = "22222222-2222-4222-8222-222222222222"
+            with WptFixtureServer(root_path) as server:
+                def request(query: str, *, method: str = "GET", alternate: bool = False) -> tuple[str, bytes]:
+                    port = server.alternate_port if alternate else server.port
+                    url = f"http://127.0.0.1:{port}{resource}?{query}"
+                    with urlopen(Request(url, method=method), timeout=2) as response:
+                        self.assertEqual(response.status, 200)
+                        return response.headers["Content-Type"], response.read()
+
+                self.assertEqual(request(f"id={first}&count="), ("text/html", b"0"))
+                self.assertEqual(request(f"id={first}"), ("text/css", b"body {color: red;}"))
+                self.assertEqual(request(f"id={first}", alternate=True), ("text/css", b"body {color: red;}"))
+                self.assertEqual(request(f"id={first}", method="HEAD"), ("text/css", b""))
+                self.assertEqual(request(f"id={second}"), ("text/css", b"body {color: red;}"))
+                self.assertEqual(request(f"id={first}&count=foo"), ("text/html", b"3"))
+                self.assertEqual(request(f"id={second}&count=foo"), ("text/html", b"1"))
+                self.assertEqual(request(f"id={first}&count=foo"), ("text/html", b"0"))
+                self.assertEqual(request(f"id={first}"), ("text/css", b"body {color: red;}"))
+                self.assertEqual(request(f"id={first}&count=foo"), ("text/html", b"1"))
+
     def test_fixture_server_parses_fetch_status_parameters_as_bytes(self) -> None:
         self.assertEqual(_fetch_status_response(""), (200, "OMG", "", b""))
         self.assertEqual(

moli-benchmark/wpt-cross-current/passed-cases.txt

@@ -6020,6 +6020,7 @@ html/semantics/document-metadata/the-base-element/base_target_does_not_affect_lo
 html/semantics/document-metadata/the-link-element/attr-link-fetchpriority.html
 html/semantics/document-metadata/the-link-element/link-href-attribute-crash.html
 html/semantics/document-metadata/the-link-element/link-load-event.html
+html/semantics/document-metadata/the-link-element/link-multiple-load-events.html
 html/semantics/document-metadata/the-link-element/link-rel-attribute-tokenization.html
 html/semantics/document-metadata/the-link-element/link-rel-attribute.html
 html/semantics/document-metadata/the-link-element/link-rellist.html