Backed out changeset 99cf11868f47 (bug 1375243) for failures in browser_bug413915.js a=backout

MozReview-Commit-ID: 3JyS99zK3z2

browser/modules/Feeds.jsm

@@ -75,9 +75,14 @@ this.Feeds = {
     }
 
     if (aIsFeed) {
+      // re-create the principal as it may be a CPOW.
+      // once this can't be a CPOW anymore, we should just use aPrincipal instead
+      // of creating a new one.
+      let principalURI = BrowserUtils.makeURIFromCPOW(aPrincipal.URI);
+      let principalToCheck =
+        Services.scriptSecurityManager.createCodebasePrincipal(principalURI, aPrincipal.originAttributes);
       try {
-        let href = BrowserUtils.makeURI(aLink.href, aLink.ownerDocument.characterSet);
-        BrowserUtils.urlSecurityCheck(href, aPrincipal,
+        BrowserUtils.urlSecurityCheck(aLink.href, principalToCheck,
                                       Ci.nsIScriptSecurityManager.DISALLOW_INHERIT_PRINCIPAL);
         return type || "application/rss+xml";
       } catch (ex) {