Use configurable imports to avoid having two versions of everything.

R=floitsch@google.com

Review URL: https://codereview.chromium.org//2353933002 .

Committed: https://github.com/dart-lang/resource/commit/f1c6229ffdb33a7f274fa819ebe5f0ca493ba3c5
Committed: https://github.com/dart-lang/resource/commit/799a627d802b42b244273c35b67f3504ea83f008
diff --git a/lib/src/io_html.dart b/lib/src/io_html.dart
index 2896967..420815c 100644
--- a/lib/src/io_html.dart
+++ b/lib/src/io_html.dart
@@ -3,9 +3,9 @@
 // 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* {