Fetch policies asynchronously for about: and javascript: URLs.

src/content/staticNS.js

@@ -40,13 +40,14 @@
         , document.documentElement.outerHTML, // DEV_ONLY
         document.domain, document.baseURI, window.isSecureContext // DEV_ONLY
       );
+
+      if (!/^(?:file|ftp|https?):/i.test(url)) {
         if (/^(javascript|about):/.test(url)) {
           url = document.readyState === "loading"
           ? document.baseURI
           : `${window.isSecureContext ? "https" : "http"}://${document.domain}`;
           debug("Fetching policy for actual URL %s (was %s)", url, document.URL);
         }
-      if (!/^(?:file|ftp|https?):/i.test(url)) {
         (async () => {
           let policy;
           try {