don't run dart gen on JS patch code

test/dart_codegen/expect/core/double.dart

Index: test/dart_codegen/expect/core/double.dart
diff --git a/test/dart_codegen/expect/core/double.dart b/test/dart_codegen/expect/core/double.dart
index 54c5b263de83e8a22c85b11ee0a0ea11fabc2f57..6072c1b8f62f04916780aa901948625feb143883 100644
--- a/test/dart_codegen/expect/core/double.dart
+++ b/test/dart_codegen/expect/core/double.dart
@@ -25,9 +25,5 @@ abstract class double extends num {
   double ceilToDouble();
   double truncateToDouble();
   String toString();
-  static double parse(String source, [double onError(String source)]) {
-    return ((__x10) => DDC$RT.cast(__x10, dynamic, double, "CastGeneral",
-        """line 206, column 12 of dart:core/double.dart: """, __x10 is double,
-        true))(Primitives.parseDouble(source, onError));
-  }
+  external static double parse(String source, [double onError(String source)]);
 }