Update pub usage of '127.0.0.1'.

sdk/lib/_internal/pub/lib/src/oauth2.dart

Index: sdk/lib/_internal/pub/lib/src/oauth2.dart
diff --git a/sdk/lib/_internal/pub/lib/src/oauth2.dart b/sdk/lib/_internal/pub/lib/src/oauth2.dart
index e4b8ee07283706bd99133c3ca4c3774e1d2243ca..56b14949d937cb5071e9c5a65aadcf7338d43023 100644
--- a/sdk/lib/_internal/pub/lib/src/oauth2.dart
+++ b/sdk/lib/_internal/pub/lib/src/oauth2.dart
@@ -169,7 +169,7 @@ Future<Client> _authorize() {
   // Spin up a one-shot HTTP server to receive the authorization code from the
   // Google OAuth2 server via redirect. This server will close itself as soon as
   // the code is received.
-  return SafeHttpServer.bind('127.0.0.1', 0).then((server) {
+  return SafeHttpServer.bind('localhost', 0).then((server) {
     var authUrl = grant.getAuthorizationUrl(
         Uri.parse('http://localhost:${server.port}'), scopes: _scopes);