Remove deprecated string features.

utils/peg/pegparser.dart

Index: utils/peg/pegparser.dart
diff --git a/utils/peg/pegparser.dart b/utils/peg/pegparser.dart
index 9072e2d315f92396fad80b55320f05077c83ff30..e389e8d1e5b82eab7e56b0828c44603578f7c244 100644
--- a/utils/peg/pegparser.dart
+++ b/utils/peg/pegparser.dart
@@ -62,7 +62,7 @@ _Rule CHAR([characters]) {
 
   // Find the range of character codes and construct an array of flags for codes
   // within the range.
-  List<int> codes = characters.charCodes;
+  List<int> codes = characters.codeUnits;
   codes.sort((a, b) => a < b ? -1 : a > b ? 1 : 0);
   int lo = codes[0];
   int hi = codes[codes.length - 1];
@@ -452,7 +452,7 @@ class _CharCodeRule extends _Rule {
   _match(_ParserState state, int pos) {
     if (pos == state._end)
       return null;
-    int code = state._text.charCodeAt(pos);
+    int code = state._text.codeUnitAt(pos);
     if (_predicate(code))
       return [pos + 1, null];
     return null;
@@ -511,7 +511,7 @@ class _StringRule extends _Rule implements _Expectable {
     if (pos + _len > state._end)
       return null;
     for (int i = 0; i < _len; i++) {
-      if (state._text.charCodeAt(pos + i) != _string.charCodeAt(i))
+      if (state._text.codeUnitAt(pos + i) != _string.codeUnitAt(i))
         return null;
     }
     return [pos + _len, null];