Remove explicit delayed futures in dart:io.

sdk/lib/io/websocket_impl.dart

Index: sdk/lib/io/websocket_impl.dart
diff --git a/sdk/lib/io/websocket_impl.dart b/sdk/lib/io/websocket_impl.dart
index 3842b605569cb0d769fe29550f4c7aa4a4234ba0..3cef0ad606f7c15279ad9d2e3311d67a442466af 100644
--- a/sdk/lib/io/websocket_impl.dart
+++ b/sdk/lib/io/websocket_impl.dart
@@ -585,13 +585,12 @@ class _WebSocketConsumer implements StreamConsumer {
 
   bool _done([error]) {
     if (_completer == null) return false;
-    var tmp = _completer;
-    _completer = null;
     if (error != null) {
-      tmp.completeError(error);
+      _completer.completeError(error);
     } else {
-      tmp.complete(webSocket);
+      _completer.complete(webSocket);
     }
+    _completer = null;
     return true;
   }