cleanup patch generation to preseve comments and remove @patch

test/dart_codegen/expect/collection/linked_hash_map.dart

 part of dart.collection;
 
 abstract class LinkedHashMap<K, V> implements HashMap<K, V> {
-  @patch factory LinkedHashMap({bool equals(K key1, K key2),
-      int hashCode(K key), bool isValidKey(potentialKey)}) {
+  factory LinkedHashMap({bool equals(K key1, K key2), int hashCode(K key),
+      bool isValidKey(potentialKey)}) {
     if (isValidKey == null) {
       if (hashCode == null) {
         if (equals == null) {
           return new _LinkedHashMap<K, V>();
         }
         hashCode = _defaultHashCode;
       } else {
         if (identical(identityHashCode, hashCode) &&
             identical(identical, equals)) {
           return new _LinkedIdentityHashMap<K, V>();
         }
         if (equals == null) {
           equals = _defaultEquals;
         }
       }
     } else {
       if (hashCode == null) {
         hashCode = _defaultHashCode;
       }
       if (equals == null) {
         equals = _defaultEquals;
       }
     }
     return new _LinkedCustomHashMap<K, V>(equals, hashCode, isValidKey);
   }
-  @patch factory LinkedHashMap.identity() = _LinkedIdentityHashMap<K, V>;
+  factory LinkedHashMap.identity() = _LinkedIdentityHashMap<K, V>;
   factory LinkedHashMap.from(Map other) {
     LinkedHashMap<K, V> result = new LinkedHashMap<K, V>();
     other.forEach((k, v) {
       result[k] = DDC$RT.cast(v, dynamic, V, "CastGeneral",
-          """line 65, column 40 of dart:collection/linked_hash_map.dart: """,
+          """line 99, column 40 of dart:collection/linked_hash_map.dart: """,
           v is V, false);
     });
     return result;
   }
   factory LinkedHashMap.fromIterable(Iterable iterable,
       {K key(element), V value(element)}) {
     LinkedHashMap<K, V> map = new LinkedHashMap<K, V>();
     Maps._fillMapWithMappedIterable(map, iterable, key, value);
     return map;
   }
   factory LinkedHashMap.fromIterables(Iterable<K> keys, Iterable<V> values) {
     LinkedHashMap<K, V> map = new LinkedHashMap<K, V>();
     Maps._fillMapWithIterables(map, keys, values);
     return map;
   }
 }