Revert "Fix remaining strong-mode warnings and errors in dart:io."

sdk/lib/io/bytes_builder.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.
 
 part of dart.io;
 
 /**
  * Builds a list of bytes, allowing bytes and lists of bytes to be added at the
  * end.
  *
@@ skipping 135 matching lines @@
     x |= x >> 4;
     x |= x >> 8;
     x |= x >> 16;
     return x + 1;
   }
 }
 
 
 class _BytesBuilder implements BytesBuilder {
   int _length = 0;
-  final List<Uint8List> _chunks = [];
+  final _chunks = <List<int>>[];
 
   void add(List<int> bytes) {
-    Uint8List typedBytes;
-    if (bytes is Uint8List) {
-      typedBytes = bytes;
-    } else {
+    if (bytes is! Uint8List) {
       bytes = new Uint8List.fromList(bytes);
     }
-    _chunks.add(typedBytes);
-    _length += typedBytes.length;
+    _chunks.add(bytes);
+    _length += bytes.length;
   }
 
   void addByte(int byte) { add([byte]); }
 
   List<int> takeBytes() {
     if (_chunks.length == 0) return new Uint8List(0);
     if (_chunks.length == 1) {
       var buffer = _chunks.single;
       clear();
       return buffer;
@@ skipping 23 matching lines @@
 
   bool get isEmpty => _length == 0;
 
   bool get isNotEmpty => _length != 0;
 
   void clear() {
     _length = 0;
     _chunks.clear();
   }
 }