js_runtime: LinkedHashMap._makeEmpty may be removed

sdk/lib/_internal/js_runtime/lib/collection_patch.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.
 
 // Patch file for dart:collection classes.
 import 'dart:_foreign_helper' show JS;
 import 'dart:_js_helper'
     show
         fillLiteralMap,
         InternalMap,
@@ skipping 528 matching lines @@
   // Private factory constructor called by generated code for map literals.
   @NoThrows()
   @NoInline()
   @NoSideEffects()
   factory LinkedHashMap._empty() {
     return new JsLinkedHashMap<K, V>.es6();
   }
 
   // Private factory static function called by generated code for map literals.
   // This version is for map literals without type parameters.
+  @NoThrows()
   @NoInline()
+  @NoSideEffects()
   static _makeEmpty() => new JsLinkedHashMap();
 
   // Private factory static function called by generated code for map literals.
   // This version is for map literals without type parameters.
   @NoInline()
   static _makeLiteral(keyValuePairs) =>
       fillLiteralMap(keyValuePairs, new JsLinkedHashMap());
 }
 
 class _LinkedIdentityHashMap<K, V> extends JsLinkedHashMap<K, V> {
@@ skipping 1098 matching lines @@
     } else if (_cell == null) {
       _current = null;
       return false;
     } else {
       _current = _cell._element;
       _cell = _cell._next;
       return true;
     }
   }
 }