Update CodeUnits.

tool/input_sdk/private/js_string.dart

Index: tool/input_sdk/private/js_string.dart
diff --git a/tool/input_sdk/private/js_string.dart b/tool/input_sdk/private/js_string.dart
index d7845692842b08eb7054f84504bf674518c34df8..3a283097baabfef6a331c2fba6c1b5eb3d410701 100644
--- a/tool/input_sdk/private/js_string.dart
+++ b/tool/input_sdk/private/js_string.dart
@@ -374,7 +374,7 @@ class JSString extends Interceptor implements String, JSIndexable {
     return this + padding * delta;
   }
 
-  List<int> get codeUnits => new _CodeUnits(this);
+  List<int> get codeUnits => new CodeUnits(this);
 
   Runes get runes => new Runes(this);
 
@@ -471,16 +471,3 @@ class JSString extends Interceptor implements String, JSIndexable {
     return JS('String', '#[#]', this, index);
   }
 }
-
-/**
- * An [Iterable] of the UTF-16 code units of a [String] in index order.
- */
-class _CodeUnits extends UnmodifiableListBase<int> {
-  /** The string that this is the code units of. */
-  String _string;
-
-  _CodeUnits(this._string);
-
-  int get length => _string.length;
-  int operator[](int i) => _string.codeUnitAt(i);
-}