Make Stream.where, etc., be documented as inheriting broadcast state.

tests/lib/async/stream_timeout_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.
 
 import "dart:async";
 import "package:unittest/unittest.dart";
 
 main() {
   const ms5 = const Duration(milliseconds: 5);
   const twoSecs = const Duration(seconds: 2);
@@ skipping 49 matching lines @@
                onError: expectAsync((e, s) {
                  expect(ctr, 2);
                  expect(e, new isInstanceOf<TimeoutException>());
                }));
     c..add(42)..add(42);  // No close, timeout after two events.
   });
 
   test("broadcast stream timeout",  () {
     StreamController c = new StreamController.broadcast();
     Stream tos = c.stream.timeout(ms5);
-    expect(tos.isBroadcast, false);
+    expect(tos.isBroadcast, true);
     tos.handleError(expectAsync((e, s) {
       expect(e, new isInstanceOf<TimeoutException>());
       expect(s, null);
     })).listen((v){ fail("Unexpected event"); });
   });
 
   test("asBroadcast stream timeout",  () {
     StreamController c = new StreamController.broadcast();
     Stream tos = c.stream.asBroadcastStream().timeout(ms5);
-    expect(tos.isBroadcast, false);
+    expect(tos.isBroadcast, true);
     tos.handleError(expectAsync((e, s) {
       expect(e, new isInstanceOf<TimeoutException>());
       expect(s, null);
     })).listen((v){ fail("Unexpected event"); });
   });
 
   test("mapped stream timeout",  () {
     StreamController c = new StreamController();
     Stream tos = c.stream.map((x) => 2 * x).timeout(ms5);
     expect(tos.isBroadcast, false);
@@ skipping 82 matching lines @@
       fail("Timeout not prevented by close");
     });
     var subscription = tos.listen((_) {}, onDone: expectAsync((){}));
     subscription.pause();
     new Timer(twoSecs, () {
       c.close();
       subscription.resume();
     });
   });
 }