Replace old utf8 decoder with new one.

tests/lib/convert/utf8_test.dart

Index: tests/lib/convert/utf8_test.dart
diff --git a/tests/lib/utf/utf8_test.dart b/tests/lib/convert/utf8_test.dart
similarity index 95%
copy from tests/lib/utf/utf8_test.dart
copy to tests/lib/convert/utf8_test.dart
index 3fdd8a84d4c2fff294e074ade1298803467c0347..4fa02970df59d891df5c7f068684261bd7ac50ed 100644
--- a/tests/lib/utf/utf8_test.dart
+++ b/tests/lib/convert/utf8_test.dart
@@ -4,9 +4,9 @@
 
 library utf8_test;
 import "package:expect/expect.dart";
-import 'dart:utf';
+import 'dart:convert';
 
-String decode(List<int> bytes) => decodeUtf8(bytes);
+String decode(List<int> bytes) => new Utf8Decoder().convert(bytes);
 
 main() {
   // Google favorite: "Îñţérñåţîöñåļîžåţîờñ".