don't run dart gen on JS patch code

test/dart_codegen/expect/core/core

Index: test/dart_codegen/expect/core/core
diff --git a/test/dart_codegen/expect/core/core b/test/dart_codegen/expect/core/core
index 65986b46d4094505d0d7181efd187a2f561571c9..190cefdcda5a49d7bfeb8369dce4bcb31797b94f 100644
--- a/test/dart_codegen/expect/core/core
+++ b/test/dart_codegen/expect/core/core
@@ -7,7 +7,6 @@ import "dart:_internal" hide Symbol;
 import "dart:_internal" as internal show Symbol;
 import "dart:convert" show UTF8, LATIN1, Encoding;
 import "dart:math" show Random;
-import "dart:_internal" as _symbol_dev;
 part "annotations.dart";
 part "bool.dart";
 part "comparable.dart";
@@ -41,18 +40,3 @@ part "string_sink.dart";
 part "symbol.dart";
 part "type.dart";
 part "uri.dart";
-
-String _symbolToString(Symbol symbol) => _symbol_dev.Symbol.getName(DDC$RT.cast(
-    symbol, Symbol, Symbol, "CastGeneral",
-    """line 196, column 69 of dart:core: """, symbol is Symbol, true));
-_symbolMapToStringMap(Map<Symbol, dynamic> map) {
-  if (map == null) return null;
-  var result = new Map<String, dynamic>();
-  map.forEach((Symbol key, value) {
-    result[_symbolToString(key)] = value;
-  });
-  return result;
-}
-class _ListConstructorSentinel extends JSInt {
-  const _ListConstructorSentinel();
-}