Work around issue 6984.

utils/pub/oauth2.dart

Index: utils/pub/oauth2.dart
diff --git a/utils/pub/oauth2.dart b/utils/pub/oauth2.dart
index 49de1c0bcf673debc769ca7a8e144176c20b4238..4960dced1c5b89fedd11fee6457c3a951070e7c5 100644
--- a/utils/pub/oauth2.dart
+++ b/utils/pub/oauth2.dart
@@ -157,9 +157,13 @@ Future<Client> _authorize() {
       if (queryString == null) queryString = '';
       response.statusCode = 302;
       response.headers.set('location', 'http://pub.dartlang.org/authorized');
-      response.outputStream.close();
+      return Futures.wait([
+        closeHttpResponse(request, response),
+        grant.handleAuthorizationResponse(queryToMap(queryString))
+      ]);
+    }).transform((results) {
       server.close();
-      return grant.handleAuthorizationResponse(queryToMap(queryString));
+      return results[1];
     }), completer);
   });
   server.listen('127.0.0.1', 0);