cleanup patch generation to preseve comments and remove @patch

test/dart_codegen/expect/core/bool.dart

Index: test/dart_codegen/expect/core/bool.dart
diff --git a/test/dart_codegen/expect/core/bool.dart b/test/dart_codegen/expect/core/bool.dart
index d86b1c20a862b878cd26ce7c770df0a35836a9c1..a83a795a335647ce63beab71288dfc8be2eeabac 100644
--- a/test/dart_codegen/expect/core/bool.dart
+++ b/test/dart_codegen/expect/core/bool.dart
@@ -1,7 +1,7 @@
 part of dart.core;
 
 class bool {
-  @patch factory bool.fromEnvironment(String name, {bool defaultValue: false}) {
+  factory bool.fromEnvironment(String name, {bool defaultValue: false}) {
     throw new UnsupportedError(
         'bool.fromEnvironment can only be used as a const constructor');
   }