add test that ;secure Set-Cookie header doesn't affect previous cooki…

…e's value

The Ignore name- and value-less `Set-Cookie: ; bar` test was also failing
before, but due to bug 1848226 it wasn't removed in bug 1892748.

Differential Revision: https://phabricator.services.mozilla.com/D213551

bugzilla-url: https://bugzilla.mozilla.org/show_bug.cgi?id=1901325
gecko-commit: a60507c6dfe7fff34a6fd90d21f5cc9a5eb21f06
gecko-reviewers: edgul

cookies/attributes/secure.https.html

@@ -54,7 +54,12 @@
           cookie: "test=8;       Secure     ;",
           expected: "test=8",
           name: "Set cookie for space Secure with ;",
-        }
+        },
+        {
+          cookie: ["testa9a=x; secure; ", "; secure", "testa9b=y; secure;"],
+          expected: "testa9a=x; testa9b=y",
+          name: "Ignore name- and value-less `Set-Cookie: ; secure`",
+        },
       ];
 
       for (const test of secureTests) {