When a connection is upgraded, don't return it as idle.

tests/standalone/io/http_detach_socket_test.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 //
 // VMOptions=
 // VMOptions=--short_socket_read
 // VMOptions=--short_socket_write
 // VMOptions=--short_socket_read --short_socket_write
 
 import "package:expect/expect.dart";
@@ skipping 127 matching lines @@
                             body.toString());
               client.close();
             });
           socket.write("Some data");
           socket.close();
         });
       });
   });
 }
 
+void testUpgradedConnection() {
+  HttpServer.bind("127.0.0.1", 0).then((server) {
+    server.listen((request) {
+      request.response.headers.set('connection', 'upgrade');

[Søren Gjesse, 2014/06/02 07:30:52]

Should this test also detach the socket on this side, and maybe send some data?

[Anders Johnsen, 2014/06/02 08:00:35]

Done.

+      request.response.close();
+    });
+
+    var client = new HttpClient();
+    client.userAgent = null;
+    client.get("127.0.0.1", server.port, "/")
+      .then((request) {
+        request.headers.set('upgrade', 'mine');
+        return request.close();
+      })
+      .then((response) {
+        client.get("127.0.0.1", server.port, "/")
+            .then((request) {
+              response.detachSocket().then((socket) {
+                // We are testing that we can detach the socket, even though
+                // we made a new connection (testing it was not reused).
+                request.close().then((response) {
+                  response.drain().then((_) {
+                    server.close();
+                  });
+                  socket.destroy();
+                });
+              });
+            });
+      });
+  });
+}
+
 void main() {
   testServerDetachSocket();
   testServerDetachSocketNoWriteHeaders();
   testBadServerDetachSocket();
   testClientDetachSocket();
+  testUpgradedConnection();
 }