Avoid the _onSubscriptionStateChange being called twice in some cases.

tests/lib/async/stream_from_iterable_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.
 
 // Test merging streams.
 library dart.test.stream_from_iterable;
 
 import "dart:async";
 import '../../../pkg/unittest/lib/unittest.dart';
 import 'event_helper.dart';
@@ skipping 18 matching lines @@
   new IterableTest([]).run();
   new IterableTest([1]).run();
   new IterableTest([1, "two", true, null]).run();
   new IterableTest<int>([1, 2, 3, 4]).run();
   new IterableTest<String>(["one", "two", "three", "four"]).run();
   new IterableTest<int>(new Iterable<int>.generate(1000, (i) => i)).run();
   new IterableTest<String>(new Iterable<int>.generate(1000, (i) => i)
                                             .mappedBy((i) => "$i")).run();
 
   Iterable<int> iter = new Iterable.generate(25, (i) => i * 2);
-  new Stream.fromIterable(iter).toList().then(expectAsync1((actual) {
-    List expected = iter.toList();
-    Expect.equals(25, expected.length);
-    Expect.listEquals(expected, actual);
-  }));
 
-  new Stream.fromIterable(iter)
-    .mappedBy((i) => i * 3)
-    .toList()
-    .then(expectAsync1((actual) {
-       List expected = iter.mappedBy((i) => i * 3).toList();
-       Expect.listEquals(expected, actual);
+  test("iterable-toList", () {
+    new Stream.fromIterable(iter).toList().then(expectAsync1((actual) {
+      List expected = iter.toList();
+      Expect.equals(25, expected.length);
+      Expect.listEquals(expected, actual);
     }));
+  });
 
-  {  // Test pause.
+  test("iterable-mapped-toList", () {
+    new Stream.fromIterable(iter)
+      .mappedBy((i) => i * 3)
+      .toList()
+      .then(expectAsync1((actual) {
+         List expected = iter.mappedBy((i) => i * 3).toList();
+         Expect.listEquals(expected, actual);
+      }));
+  });
+
+  test("iterable-paused", () {
     Stream stream = new Stream.fromIterable(iter);
     Events actual = new Events();
     StreamSubscription subscription;
     subscription = stream.listen((int value) {
       actual.add(value);
       // Do a 10 ms pause during the playback of the iterable.
       if (value == 20) { subscription.pause(new Future.delayed(10, () {})); }
     }, onDone: expectAsync0(() {
       actual.close();
       Events expected = new Events.fromIterable(iter);
       Expect.listEquals(expected.events, actual.events);
     }));
-  }
+  });
 }