cleanup patch generation to preseve comments and remove @patch

test/generated_sdk/lib/async/deferred_load.dart

 // Copyright (c) 2013, 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.
 
 part of dart.async;
 
 /**
  * Indicates that loading of [libraryName] is deferred.
  *
  * This class is obsolete. Instead use the syntax:
  * import "library.dart" deferred as prefix;
  */
 @Deprecated("Dart sdk v. 1.8")
 class DeferredLibrary {
   final String libraryName;
   final String uri;
 
   const DeferredLibrary(this.libraryName, {this.uri});
 
-  @patch
+  /**
+   * Ensure that [libraryName] has been loaded.
+   *
+   * If the library fails to load, the Future will complete with a
+   * DeferredLoadException.
+   */
   Future<Null> load() {
     throw 'DeferredLibrary not supported. '
           'please use the `import "lib.dart" deferred as lib` syntax.';
   }
 }
 
 /**
  * Thrown when a deferred library fails to load.
  */
 class DeferredLoadException implements Exception {
   DeferredLoadException(String this._s);
   String toString() => "DeferredLoadException: '$_s'";
   final String _s;
 }