Revert "Reapply "New implementation of {,Linked}Hash{Set,Map}.""

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 70c6c532f1522667a5897d0999664ddb54472b59..224c1e72b629b2637a08323e0e72e5b0d67affb0 100644
--- a/sdk/lib/io/http_impl.dart
+++ b/sdk/lib/io/http_impl.dart
@@ -1917,15 +1917,14 @@ class _HttpClient implements HttpClient {
 
   void shutdown({bool force: false}) {
     if (force) _closeQueue.shutdown();
-    new Map.from(_openSockets).forEach(
-        (String key, Queue<_SocketConnection> connections) {
+    _openSockets.forEach((String key, Queue<_SocketConnection> connections) {
       while (!connections.isEmpty) {
         _SocketConnection socketConn = connections.removeFirst();
         socketConn._socket.close();
       }
     });
     if (force) {
-      _activeSockets.toList().forEach((_SocketConnection socketConn) {
+      _activeSockets.forEach((_SocketConnection socketConn) {
         socketConn._httpClientConnection._onClientShutdown();
         socketConn._close();
       });