don't run dart gen on JS patch code

test/dart_codegen/expect/core/iterable.dart

 part of dart.core;
 
 abstract class Iterable<E> {
   const Iterable();
   factory Iterable.generate(int count, [E generator(int index)]) {
     if (count <= 0) return new EmptyIterable<E>();
     return new _GeneratorIterable<E>(count, generator);
   }
   Iterator<E> get iterator;
   Iterable map(f(E element));
@@ skipping 60 matching lines @@
   final _Generator<E> _generator;
   int _index;
   E _current;
   _GeneratorIterator(this._index, this._end, this._generator);
   bool moveNext() {
     if (_index < _end) {
       _current = _generator(_index);
       _index++;
       return true;
     } else {
-      _current = ((__x25) => DDC$RT.cast(__x25, Null, E, "CastLiteral",
-          """line 360, column 18 of dart:core/iterable.dart: """, __x25 is E,
+      _current = ((__x7) => DDC$RT.cast(__x7, Null, E, "CastLiteral",
+          """line 360, column 18 of dart:core/iterable.dart: """, __x7 is E,
           false))(null);
       return false;
     }
   }
   E get current => _current;
 }
 abstract class BidirectionalIterator<E> implements Iterator<E> {
   bool movePrevious();
 }