Make String.charCodes a getter.

tests/standalone/io/http_read_test.dart

Index: tests/standalone/io/http_read_test.dart
diff --git a/tests/standalone/io/http_read_test.dart b/tests/standalone/io/http_read_test.dart
index 3a0c8495f0b86da090dbc3801a23c5727fcd175c..15e2606659602e785e4e2469a56bf6bea3ef9a15 100644
--- a/tests/standalone/io/http_read_test.dart
+++ b/tests/standalone/io/http_read_test.dart
@@ -173,7 +173,7 @@ void testReadInto(bool chunkedEncoding) {
           request.outputStream.writeString(data.substring(10, data.length));
         } else {
           request.contentLength = data.length;
-          request.outputStream.write(data.charCodes());
+          request.outputStream.write(data.charCodes);
         }
         request.outputStream.close();
       };
@@ -227,7 +227,7 @@ void testReadShort(bool chunkedEncoding) {
           request.outputStream.writeString(data.substring(10, data.length));
         } else {
           request.contentLength = data.length;
-          request.outputStream.write(data.charCodes());
+          request.outputStream.write(data.charCodes);
         }
         request.outputStream.close();
       };