cleanup patch generation to preseve comments and remove @patch

test/generated_sdk/lib/math/random.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.math;
 
 /**
  * A generator of random bool, int, or double values.
  *
  * The default implementation supplies a stream of
  * pseudo-random bits that are not suitable for cryptographic purposes.
  */
 abstract class Random {
-  @patch
+  /**
+   * Creates a random-number generator. The optional parameter [seed] is used
+   * to initialize the internal state of the generator. The implementation of
+   * the random stream can change between releases of the library.
+   */
   factory Random([int seed]) =>
       (seed == null) ? const _JSRandom() : new _Random(seed);
 
   /**
    * Generates a positive random integer uniformly distributed on the range
    * from 0, inclusive, to [max], exclusive.
    *
    * Implementation note: The default implementation supports [max] values
    * between 1 and ((1<<32) - 1) inclusive.
    */
   int nextInt(int max);
 
   /**
    * Generates a positive random floating point value uniformly distributed on
    * the range from 0.0, inclusive, to 1.0, exclusive.
    */
   double nextDouble();
 
   /**
    * Generates a random boolean value.
    */
   bool nextBool();
 }