Backing out bug 409885, since this part of Necko happens not to exist.

content/html/document/src/nsHTMLDocument.cpp

@@ -1718,16 +1718,20 @@ nsHTMLDocument::SetDomain(const nsAString& aDomain)
     return NS_ERROR_FAILURE;
   }
 
+  nsCAutoString newURIString;
+  if (NS_FAILED(uri->GetScheme(newURIString)))
+    return NS_ERROR_FAILURE;
+  nsCAutoString path;
+  if (NS_FAILED(uri->GetPath(path)))
+    return NS_ERROR_FAILURE;
+  newURIString.AppendLiteral("://");
+  AppendUTF16toUTF8(aDomain, newURIString);
+  newURIString.Append(path);
+
   nsCOMPtr<nsIURI> newURI;
-  nsresult rv = uri->Clone(getter_AddRefs(newURI));
-  NS_ENSURE_TRUE(newURI, rv);
+  if (NS_FAILED(NS_NewURI(getter_AddRefs(newURI), newURIString)))
+    return NS_ERROR_FAILURE;
 
-  rv = newURI->SetUserPass(EmptyCString());
-  NS_ENSURE_SUCCESS(rv, rv);
-
-  rv = newURI->SetHostPort(NS_ConvertUTF16toUTF8(aDomain));
-  NS_ENSURE_SUCCESS(rv, rv);
-  
   // Check new domain - must be a superdomain of the current host
   // For example, a page from foo.bar.com may set domain to bar.com,
   // but not to ar.com, baz.com, or fi.foo.bar.com.
@@ -1758,7 +1762,6 @@ nsHTMLDocument::SetDomain(const nsAString& aDomain)
     return NS_ERROR_DOM_BAD_DOCUMENT_DOMAIN;
   }
 
-  NS_TryToSetImmutable(newURI);
   return NodePrincipal()->SetDomain(newURI);
 }