Fix <meta> referrer post-insertion steps expectations

See whatwg/html#10241 for the recommendation
to change these test expectations to align with Chromium and WebKit's
behavior.

[email protected]

Bug: 40150299
Change-Id: I3cabc92c16a4cfadc6675bd156aca04c2ade64aa

dom/nodes/insertion-removing-steps/Node-append-meta-referrer-and-script-from-fragment.tentative.html

@@ -5,25 +5,37 @@
 <script src=/resources/testharnessreport.js></script>
 <script>
 promise_test(async t => {
-    const script = document.createElement("script");
-    const meta = document.createElement("meta");
-    meta.name = "referrer";
-    meta.content = "no-referrer";
-    const fragment = new DocumentFragment();
-    const done = new Promise(resolve => {
-        window.didFetch = resolve;
-    });
-    script.textContent = `
-        (async function() {
-            const response = await fetch("/html/infrastructure/urls/terminology-0/resources/echo-referrer-text.py")
-            const text = await response.text();
-            window.didFetch(text);
-        })();
-    `;
-    fragment.append(script, meta);
-    document.head.append(fragment);
-    const result = await done;
-    assert_equals(result, "");
-}, "<meta name=referrer> should apply before script, as it is an insertion step " +
-    "and not a post-insertion step");
+  const preMetaScript = document.createElement("script");
+  preMetaScript.textContent = `
+    window.preMetaScriptPromise = fetch('/html/infrastructure/urls/terminology-0/resources/echo-referrer-text.py')
+      .then(response => response.text());
+  `;
+
+  const meta = document.createElement("meta");
+  meta.name = "referrer";
+  meta.content = "no-referrer";
+
+  const postMetaScript = document.createElement("script");
+  postMetaScript.textContent = `
+    window.postMetaScriptPromise = fetch('/html/infrastructure/urls/terminology-0/resources/echo-referrer-text.py')
+      .then(response => response.text());
+  `;
+
+  const fragment = new DocumentFragment();
+  fragment.append(preMetaScript, meta, postMetaScript);
+  document.head.append(fragment);
+
+  const preMetaReferrer = await window.preMetaScriptPromise;
+  assert_equals(preMetaReferrer, location.href,
+      "preMetaReferrer is the full URL; by the time the first script runs in " +
+      "its post-insertion steps, the later-inserted meta tag has not run its " +
+      "post-insertion steps, which is where meta tags are processed");
+
+  const postMetaReferrer = await window.postMetaScriptPromise;
+  assert_equals(postMetaReferrer, "",
+      "postMetaReferrer is empty; by the time the second script runs in " +
+      "its post-insertion steps, the later-inserted meta tag has run its " +
+      "post-insertion steps, and observes the meta tag's effect");
+}, "<meta name=referrer> gets processed and applied in the post-insertion " +
+   "steps");
 </script>