- Allow implementations to hook into the Utf8Decoder.convert method.

sdk/lib/_internal/compiler/js_lib/convert_patch.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.
 
 // Patch file for dart:convert library.
 
 import 'dart:_js_helper' show patch;
 import 'dart:_foreign_helper' show JS;
 import 'dart:_interceptors' show JSExtendableArray;
 import 'dart:_internal' show MappedIterable, ListIterable;
@@ skipping 382 matching lines @@
     _sink.add(decoded);
     _sink.close();
   }
 }
 
 @patch class Utf8Decoder {
   @patch
   Converter<List<int>,dynamic> fuse(Converter<String, dynamic> next) {
     return super.fuse(next);
   }
+
+  // Currently not intercepting UTF8 decoding.
+  @patch
+  static String _convertIntercepted(bool allowMalformed, List<int> codeUnits,
+                                    int start, int end) {
+    return null;  // This call was not intercepted.
+  }
 }