Remove explicit delayed futures in dart:io.

sdk/lib/io/http_impl.dart

Index: sdk/lib/io/http_impl.dart
diff --git a/sdk/lib/io/http_impl.dart b/sdk/lib/io/http_impl.dart
index c1e10ac0d99cfef064560268e3259dac7ac700c5..c749cebd26919281acf0b576c50d0dbdfd58f954 100644
--- a/sdk/lib/io/http_impl.dart
+++ b/sdk/lib/io/http_impl.dart
@@ -580,13 +580,12 @@ class _HttpOutboundConsumer 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(_outbound);
+      _completer.complete(_outbound);
     }
+    _completer = null;
     return true;
   }