Fix dartc in optimized mode (broken in r3358).

compiler/lib/implementation/array.dart

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 class ListFactory<E> {
   factory List.from(Iterable<E> other) {
     if (other == null) {
       throw const NullPointerException();
     }
     List<E> list = new List<E>();
@@ skipping 24 matching lines @@
 
 
 class ListImplementation<T> implements List<T> native "Array" {
   // ListImplementation maps directly to a JavaScript array. If the list is
   // constructed by the ListFactory.List constructor, it has an
   // additional named property for '_isFixed'. If it is a literal, the
   // code generator will not add the property. It will be 'undefined'
   // and coerce to false.
   bool _isFixed;
 
-  T operator[](int index) {
-    if (0 <= index && index < length) {
-      return _indexOperator(index);
-    }
-    throw new IndexOutOfRangeException(index);
-  }
-
-  void operator[]=(int index, T value) {
-    if (index < 0 || length <= index) {
-      throw new IndexOutOfRangeException(index);
-    }
-    _indexAssignOperator(index, value);
-  }
+  T operator[](int index) native;
+  void operator[]=(int index, T value) native;
 
   Iterator<T> iterator() {
     if (_isFixed) {
       return new FixedSizeListIterator<T>(this);
     } else {
       return new VariableSizeListIterator<T>(this);
     }
   }
 
-  T _indexOperator(int index) native;
-  void _indexAssignOperator(int index, T value) native;
   int get length() native;
   void _setLength(int length) native;
   void _add(T value) native;
   void _removeRange(int start, int length) native;
   void _insertRange(int start, int length, T initialValue) native;
 
   void forEach(void f(T element)) {
     Collections.forEach(this, f);
   }
 
@@ skipping 190 matching lines @@
   }
 
   static List _newList(int len) native {
     return new List(len);
   }
 
   static void _throwIndexOutOfRangeException(int index) native {
     throw new IndexOutOfRangeException(index);
   }
 }