Fix Dart 1.17 strong-mode warnings.

lib/src/typed/stream.dart

Index: lib/src/typed/stream.dart
diff --git a/lib/src/typed/stream.dart b/lib/src/typed/stream.dart
index 3db9f69932e22376a305297981d88b2f67ffaaa6..afa4462d9a019f0f6843ac1938e69e0d8a5fc06d 100644
--- a/lib/src/typed/stream.dart
+++ b/lib/src/typed/stream.dart
@@ -8,6 +8,7 @@ import 'package:collection/collection.dart';
 
 import '../utils.dart';
 import 'stream_subscription.dart';
+import '../delegate/event_sink.dart';
 
 class TypeSafeStream<T> implements Stream<T> {
   final Stream _stream;
@@ -36,20 +37,19 @@ class TypeSafeStream<T> implements Stream<T> {
                   onCancel(new TypeSafeStreamSubscription<T>(subscription))));
   }
 
-  // TODO(nweiz): Give this a generic parameter when sdk#26125 is fixed.
-  Stream asyncExpand(Stream convert(T event)) =>
+  Stream/*<E>*/ asyncExpand/*<E>*/(Stream/*<E>*/ convert(T event)) =>
       _stream.asyncExpand(_validateType(convert));
 
-  // TODO(nweiz): Give this a generic parameter when sdk#26125 is fixed.
-  Stream asyncMap(convert(T event)) => _stream.asyncMap(_validateType(convert));
+  Stream/*<E>*/ asyncMap/*<E>*/(convert(T event)) =>
+      _stream.asyncMap(_validateType(convert));
 
   Stream<T> distinct([bool equals(T previous, T next)]) =>
       new TypeSafeStream<T>(_stream.distinct(equals == null
           ? null
           : (previous, next) => equals(previous as T, next as T)));
 
-  // TODO(nweiz): Give this a generic parameter when sdk#26125 is fixed.
-  Future drain([futureValue]) => _stream.drain(futureValue);
+  Future/*<E>*/ drain/*<E>*/([/*=E*/ futureValue]) =>
+      _stream.drain(futureValue);
 
   Stream/*<S>*/ expand/*<S>*/(Iterable/*<S>*/ convert(T value)) =>
       _stream.expand(_validateType(convert));
@@ -99,8 +99,10 @@ class TypeSafeStream<T> implements Stream<T> {
   Stream<T> takeWhile(bool test(T element)) =>
       new TypeSafeStream<T>(_stream.takeWhile(_validateType(test)));
 
-  Stream timeout(Duration timeLimit, {void onTimeout(EventSink sink)}) =>
-      _stream.timeout(timeLimit, onTimeout: onTimeout);
+  Stream<T> timeout(Duration timeLimit, {void onTimeout(EventSink<T> sink)}) =>
+      new TypeSafeStream<T>(_stream.timeout(
+          timeLimit,
+          onTimeout: (sink) => onTimeout(DelegatingEventSink.typed(sink))));
 
   Future<List<T>> toList() async =>
       DelegatingList.typed/*<T>*/(await _stream.toList());