Fix all strong-mode warnings.

R=jmesserly@google.com

Review URL: https://codereview.chromium.org//1975493002 .
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 48ce8e9..d67f46a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,7 @@
+## 0.2.1
+
+* Fix all strong-mode warnings.
+
 ## 0.2.0
 
 * **Breaking change**: `webSocketHandler()` now uses the
diff --git a/lib/src/web_socket_handler.dart b/lib/src/web_socket_handler.dart
index b8f94a2..73dcfef 100644
--- a/lib/src/web_socket_handler.dart
+++ b/lib/src/web_socket_handler.dart
@@ -5,6 +5,7 @@
 import 'dart:convert';
 
 import 'package:shelf/shelf.dart';
+import 'package:stream_channel/stream_channel.dart';
 import 'package:web_socket_channel/web_socket_channel.dart';
 
 /// A class that exposes a handler for upgrading WebSocket requests.
@@ -64,7 +65,9 @@
     }
 
     var protocol = _chooseProtocol(request);
-    request.hijack((channel) {
+    request.hijack((untypedChannel) {
+      var channel = (untypedChannel as StreamChannel).cast/*<List<int>>*/();
+
       var sink = UTF8.encoder.startChunkedConversion(channel.sink);
       sink.add(
           "HTTP/1.1 101 Switching Protocols\r\n"
diff --git a/pubspec.yaml b/pubspec.yaml
index 1306106..f663cdb 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,11 +1,12 @@
 name: shelf_web_socket
-version: 0.2.0
+version: 0.2.1
 author: "Dart Team <misc@dartlang.org>"
 homepage: http://github.com/dart-lang/shelf_web_socket
 description: >
   A WebSocket handler for Shelf.
 dependencies:
   shelf: ">=0.6.5 <0.8.0"
+  stream_channel: "^1.4.0"
   web_socket_channel: "^1.0.0"
 dev_dependencies:
   http: ">=0.10.0 <0.12.0"