Added implementation of String.codeUnits.

runtime/lib/string_base.dart

 // Copyright (c) 2012, 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.
 
 /**
  * [_StringBase] contains common methods used by concrete String
  * implementations, e.g., _OneByteString.
  */
 class _StringBase {
 
@@ skipping 415 matching lines @@
 
   List<int> get charCodes {
     int len = this.length;
     final result = new List<int>.fixedLength(len);
     for (int i = 0; i < len; i++) {
       result[i] = this.charCodeAt(i);
     }
     return result;
   }
 
-  Iterable<int> get codeUnits {
-    throw new UnimplementedError("String.codeUnits");
-  }
+  Iterable<int> get codeUnits => new CodeUnits(this);
 
   Runes get runes => new Runes(this);
 
   String toUpperCase() native "String_toUpperCase";
 
   String toLowerCase() native "String_toLowerCase";
 
   // Implementations of Strings methods follow below.
   static String join(Iterable<String> strings, String separator) {
     bool first = true;
@@ skipping 173 matching lines @@
     for (int g in groups) {
       result.add(group(g));
     }
     return result;
   }
 
   final int start;
   final String str;
   final String pattern;
 }