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

sdk/lib/utf/utf32.dart

Index: sdk/lib/utf/utf32.dart
diff --git a/sdk/lib/utf/utf32.dart b/sdk/lib/utf/utf32.dart
index f79e45243342f2786da556eee9567dce8b6fe204..9cbfd7aa982e14aabd5262ad3c3c6ac2257b1236 100644
--- a/sdk/lib/utf/utf32.dart
+++ b/sdk/lib/utf/utf32.dart
@@ -96,7 +96,7 @@ List<int> encodeUtf32(String str) =>
  * UTF-32BE bytes with no BOM.
  */
 List<int> encodeUtf32be(String str, [bool writeBOM = false]) {
-  List<int> utf32CodeUnits = str.charCodes();
+  List<int> utf32CodeUnits = stringToCodepoints(str);
   List<int> encoding = new List<int>(4 * utf32CodeUnits.length +
       (writeBOM ? 4 : 0));
   int i = 0;
@@ -120,7 +120,7 @@ List<int> encodeUtf32be(String str, [bool writeBOM = false]) {
  * UTF-32BE bytes with no BOM.
  */
 List<int> encodeUtf32le(String str, [bool writeBOM = false]) {
-  List<int> utf32CodeUnits = str.charCodes();
+  List<int> utf32CodeUnits = stringToCodepoints(str);
   List<int> encoding = new List<int>(4 * utf32CodeUnits.length +
       (writeBOM ? 4 : 0));
   int i = 0;