Use configurable imports to avoid having two versions of everything.

lib/src/io_html.dart

 // Copyright (c) 2016, 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" show Future, Stream;
-import "dart:convert" show Encoding, LATIN1, UTF8;
+import "dart:convert" show Encoding;
 import "dart:html";
-import "dart:typed_data" show Uint8List, ByteBuffer;
+import "dart:typed_data" show ByteBuffer;
 
 /// Reads the bytes of a URI as a stream of bytes.
 Stream<List<int>> readAsStream(Uri uri) async* {
   // TODO(lrn): Should file be run through XmlHTTPRequest too?
   if (uri.scheme == "http" || uri.scheme == "https") {
     // TODO: Stream in chunks if DOM has a way to do so.
     List<int> response = await _httpGetBytes(uri);
     yield response;
     return;
   }
@@ skipping 32 matching lines @@
 }
 
 Future<List<int>> _httpGetBytes(Uri uri) {
   return HttpRequest
       .request(uri.toString(), responseType: "arraybuffer")
       .then((request) {
     ByteBuffer data = request.response;
     return data.asUint8List();
   });
 }