Introduce code to generate summaries from an element model.

pkg/analyzer/lib/src/summary/builder.dart

 // Copyright (c) 2014, 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.
 
 /**
  * Format-agnostic infrastructure for building summary objects.
  */
 library analyzer.src.summary.builder;
 
 import 'dart:convert';
 
 /**
  * Instances of this class encapsulate the necessary state to keep track of a
  * serialized summary that is in the process of being built.
  *
  * This class is intended to be passed to the constructors of the summary
  * Builder classes.
  */
 class BuilderContext {
   /**
    * Finalize the serialized object represented by [ref] and return it in
    * serialized form as a buffer.
    */
   List<int> getBuffer(Object ref) {
-    return JSON.encode(ref).codeUnits;
+    return UTF8.encode(JSON.encode(ref));
   }
 }