Forward cancel subscription in stream pipes.

tests/language/async_star_regression_fisk_test.dart

 // Copyright (c) 2015, 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.
 
 // This test may crash dart2js.
 
 import "dart:async";
 import "package:expect/expect.dart";
 import "package:async_helper/async_helper.dart";
 
@@ skipping 16 matching lines @@
       await for(int i in fisk().take(count)) res.add(i);
     } finally {
       res.add("done");
     }
   }
 
   asyncStart();
   fugl(3).whenComplete(() => fugl(2))
       .whenComplete(() => fugl(1))
       .whenComplete(() {
-    Expect.listEquals(res,
+    Expect.listEquals(
         ["fisk 3", "+fisk", 0, 1, "-fisk", "done",
          "fisk 2", "+fisk", 0, 1, "-fisk", "done",
-         "fisk 1", "+fisk", 0, "done", "-fisk", ]);
+         "fisk 1", "+fisk", 0, "-fisk", "done"],
+        res);
     asyncEnd();
   });
 }