cleanup patch generation to preseve comments and remove @patch

test/generated_sdk/lib/core/expando.dart

 // Copyright (c) 2012, 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.core;
 
 /**
  * An [Expando] allows adding new properties to objects.
  *
  * Does not work on numbers, strings, booleans or null.
@@ skipping 12 matching lines @@
  * since they will stay alive forever.
  */
 class Expando<T> {
 
   /**
    * The name of the this [Expando] as passed to the constructor. If
    * no name was passed to the constructor, the name is [:null:].
    */
   final String name;
 
-  @patch
+  /**
+   * Creates a new [Expando]. The optional name is only used for
+   * debugging purposes and creating two different [Expando]s with the
+   * same name yields two [Expando]s that work on different properties
+   * of the objects they are used on.
+   */
   Expando([String name]) : this.name = name;
 
   /**
    * Expando toString method override.
    */
   String toString() => "Expando:$name";
 
-  @patch
+  /**
+   * Gets the value of this [Expando]'s property on the given
+   * object. If the object hasn't been expanded, the method returns
+   * [:null:].
+   *
+   * The object must not be a number, a string, a boolean or null.
+   */
   T operator[](Object object) {
     var values = Primitives.getProperty(object, _EXPANDO_PROPERTY_NAME);
     return (values == null) ? null : Primitives.getProperty(values, _getKey());
   }
 
-  @patch
+  /**
+   * Sets the value of this [Expando]'s property on the given
+   * object. Properties can effectively be removed again by setting
+   * their value to null.
+   *
+   * The object must not be a number, a string, a boolean or null.
+   */
   void operator[]=(Object object, T value) {
     var values = Primitives.getProperty(object, _EXPANDO_PROPERTY_NAME);
     if (values == null) {
       values = new Object();
       Primitives.setProperty(object, _EXPANDO_PROPERTY_NAME, values);
     }
     Primitives.setProperty(values, _getKey(), value);
   }
 
 }