Use Uint8List for byte lists in dart:convert.

sdk/lib/_internal/lib/convert_patch.dart

Index: sdk/lib/_internal/lib/convert_patch.dart
diff --git a/sdk/lib/_internal/lib/convert_patch.dart b/sdk/lib/_internal/lib/convert_patch.dart
index ec09d2477f0f1f82481526672d23d793135e106a..dd7244d10deba02ebe3b06800a77a3d368136321 100644
--- a/sdk/lib/_internal/lib/convert_patch.dart
+++ b/sdk/lib/_internal/lib/convert_patch.dart
@@ -337,10 +337,3 @@ class _JsonMap implements LinkedHashMap {
   static _newJavaScriptObject()
       => JS('=Object', 'Object.create(null)');
 }
-
-@patch
-class _Utf8Encoder {
-  // Use Uint8List when supported on all platforms.
-  @patch
-  static List<int> _createBuffer(int size) => new List<int>(size);
-}