Fix all strong-mode warnings.

lib/src/asset/internal_asset.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.
 
 library barback.asset.internal_asset;
 
 import 'dart:async';
 import 'dart:convert';
 import 'dart:typed_data';
 
+import 'package:async/async.dart';
+import 'package:collection/collection.dart';
+
 import '../serialize.dart';
 import '../utils.dart';
 import '../utils/file_pool.dart';
 import '../utils/stream_replayer.dart';
 import 'asset.dart';
 import 'asset_id.dart';
 
 /// Serialize an asset to a form that's safe to send across isolates.
 Map serializeAsset(Asset asset) {
   var id = serializeId(asset.id);
@@ skipping 24 matching lines @@
       'id': id,
       'stream': serializeStream(asset.read())
     };
   }
 }
 
 /// Deserialize an asset from the form returned by [serialize].
 Asset deserializeAsset(Map asset) {
   var id = deserializeId(asset['id']);
   switch (asset['type']) {
-    case 'binary': return new BinaryAsset(id, asset['contents']);
+    case 'binary':
+      return new BinaryAsset(
+          id, DelegatingList.typed(asset['contents'] as List));
     case 'file': return new FileAsset(id, asset['path']);
     case 'string': return new StringAsset(id, asset['contents']);
     case 'stream':
-      return new StreamAsset(id, deserializeStream(asset['stream']));
+      return new StreamAsset(
+          id, DelegatingStream.typed(deserializeStream(asset['stream'])));
     default:
       throw new FormatException('Unknown asset type "${asset['type']}".');
   }
 }
 
 /// An asset whose data is stored in a list of bytes.
 class BinaryAsset implements Asset {
   final AssetId id;
 
   final Uint8List _contents;
@@ skipping 100 matching lines @@
 
   /// A stream replayer that records and replays the contents of the input
   /// stream.
   final StreamReplayer<List<int>> _replayer;
 
   StreamAsset(this.id, Stream<List<int>> stream)
       : _replayer = new StreamReplayer(stream);
 
   Future<String> readAsString({Encoding encoding}) {
     if (encoding == null) encoding = UTF8;
-    return _replayer.getReplay().toList()
-        .then((chunks) => encoding.decode(flatten(chunks)));
+    return _replayer.getReplay().expand((chunk) => chunk).toList()
+        .then((bytes) => encoding.decode(bytes));
   }
 
   Stream<List<int>> read() => _replayer.getReplay();
 
   String toString() => "Stream";
 }