Remove deprecated string features.

tests/standalone/io/mime_multipart_parser_test.dart

Index: tests/standalone/io/mime_multipart_parser_test.dart
diff --git a/tests/standalone/io/mime_multipart_parser_test.dart b/tests/standalone/io/mime_multipart_parser_test.dart
index 122e0754cf9ed997e43d64d15928487c2c923f76..199af84797fc9c9d1d10a4aa12d96fb4cfe5e1a6 100644
--- a/tests/standalone/io/mime_multipart_parser_test.dart
+++ b/tests/standalone/io/mime_multipart_parser_test.dart
@@ -42,7 +42,7 @@ void testParse(String message,
       if (expectedParts[partCount] != null) {
         List<int> expectedPart;
         if (expectedParts[partCount] is String) {
-          expectedPart = expectedParts[partCount].charCodes;
+          expectedPart = expectedParts[partCount].codeUnits;
         } else {
           expectedPart = expectedParts[partCount];
         }
@@ -78,7 +78,7 @@ void testParse(String message,
 
   // Test parsing the data three times delivering the data in
   // different chunks.
-  List<int> data = message.charCodes;
+  List<int> data = message.codeUnits;
   testWrite(data);
   testWrite(data, 10);
   testWrite(data, 2);