Add some support for the code-point code-unit distinction.

sdk/lib/utf/utf32.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.
 
 /**
  * Decodes the UTF-32 bytes as an iterable. Thus, the consumer can only convert
  * as much of the input as needed. Determines the byte order from the BOM,
  * or uses big-endian as a default. This method always strips a leading BOM.
  * Set the replacementCharacter to null to throw an ArgumentError
  * rather than replace the bad value.
@@ skipping 78 matching lines @@
  * bytes with a big-endian byte-order-marker.
  */
 List<int> encodeUtf32(String str) =>
     encodeUtf32be(str, true);
 
 /**
  * Produce a list of UTF-32BE encoded bytes. By default, this method produces
  * UTF-32BE bytes with no BOM.
  */
 List<int> encodeUtf32be(String str, [bool writeBOM = false]) {
-  List<int> utf32CodeUnits = stringToCodepoints(str);
+  List<int> utf32CodeUnits = str.charCodes();
   List<int> encoding = new List<int>(4 * utf32CodeUnits.length +
       (writeBOM ? 4 : 0));
   int i = 0;
   if (writeBOM) {
     encoding[i++] = 0;
     encoding[i++] = 0;
     encoding[i++] = UNICODE_UTF_BOM_HI;
     encoding[i++] = UNICODE_UTF_BOM_LO;
   }
   for (int unit in utf32CodeUnits) {
     encoding[i++] = (unit >> 24) & UNICODE_BYTE_ZERO_MASK;
     encoding[i++] = (unit >> 16) & UNICODE_BYTE_ZERO_MASK;
     encoding[i++] = (unit >> 8) & UNICODE_BYTE_ZERO_MASK;
     encoding[i++] = unit & UNICODE_BYTE_ZERO_MASK;
   }
   return encoding;
 }
 
 /**
  * Produce a list of UTF-32LE encoded bytes. By default, this method produces
  * UTF-32BE bytes with no BOM.
  */
 List<int> encodeUtf32le(String str, [bool writeBOM = false]) {
-  List<int> utf32CodeUnits = stringToCodepoints(str);
+  List<int> utf32CodeUnits = str.charCodes();
   List<int> encoding = new List<int>(4 * utf32CodeUnits.length +
       (writeBOM ? 4 : 0));
   int i = 0;
   if (writeBOM) {
     encoding[i++] = UNICODE_UTF_BOM_LO;
     encoding[i++] = UNICODE_UTF_BOM_HI;
     encoding[i++] = 0;
     encoding[i++] = 0;
   }
   for (int unit in utf32CodeUnits) {
@@ skipping 176 matching lines @@
     value += (utf32EncodedBytesIterator.next() << 24);
     return value;
   }
 }
 
 bool _validCodepoint(int codepoint) {
   return (codepoint >= 0 && codepoint < UNICODE_UTF16_RESERVED_LO) ||
       (codepoint > UNICODE_UTF16_RESERVED_HI &&
       codepoint < UNICODE_VALID_RANGE_MAX);
 }