Suppress extra cast

tool/input_sdk/patch/core_patch.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.
 
 // Patch file for dart:core classes.
 import "dart:_internal" as _symbol_dev;
 import 'dart:_interceptors';
 import 'dart:_js_helper' show patch,
                               checkInt,
                               getRuntimeType,
@@ skipping 251 matching lines @@
     List<E> list = new List<E>();
     for (var e in elements) {
       list.add(e);
     }
     if (growable) return list;
     return makeListFixedLength/*<E>*/(list);
   }
 
   @patch
   factory List.unmodifiable(Iterable elements) {
-    List result = new List<E>.from(elements, growable: false);
+    var result = new List<E>.from(elements, growable: false);
     return makeFixedListUnmodifiable/*<E>*/(result);
   }
 }
 
 
 @patch
 class String {
   @patch
   factory String.fromCharCodes(Iterable<int> charCodes,
                                [int start = 0, int end]) {
@@ skipping 188 matching lines @@
       return getTraceFromException(error);
     }
     // Fallback if Error.captureStackTrace does not exist.
     try {
       throw '';
     } catch (_, stackTrace) {
       return stackTrace;
     }
   }
 }