Remove deprecated string features.

sdk/lib/io/base64.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.
 
 part of dart.io;
 
 class _Base64 {
   static const List<String> _encodingTable = const [
       'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O',
       'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd',
@@ skipping 50 matching lines @@
 
   /**
    * Base64 transfer decoding for MIME (RFC 2045).
    */
   static List<int> _decode(String data) {
     List<int> result = new List<int>();
     int padCount = 0;
     int charCount = 0;
     int value = 0;
     for (int i = 0; i < data.length; i++) {
-      int char = data.charCodeAt(i);
+      int char = data.codeUnitAt(i);
       if (65 <= char && char <= 90) {  // "A" - "Z".
         value = (value << 6) | char - 65;
         charCount++;
       } else if (97 <= char && char <= 122) { // "a" - "z".
         value = (value << 6) | char - 97 + 26;
         charCount++;
       } else if (48 <= char && char <= 57) {  // "0" - "9".
         value = (value << 6) | char - 48 + 52;
         charCount++;
       } else if (char == 43) {  // "+".
@@ skipping 15 matching lines @@
         if (padCount == 0) {
           result.add(value & 0xFF);
         }
         charCount = 0;
         value = 0;
       }
     }
     return result;
   }
 }