Don't use ES6 map if browser has no Map

sdk/lib/_internal/compiler/js_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, NoInline, NoSideEffects, NoThrows, patch,
     JsLinkedHashMap, LinkedHashMapCell, LinkedHashMapKeyIterable,
     LinkedHashMapKeyIterator;
@@ skipping 536 matching lines @@
 }
 
 class _LinkedIdentityHashMap<K, V> extends JsLinkedHashMap<K, V> {
   static bool get _supportsEs6Maps {
     return JS('returns:bool;depends:none;effects:none;throws:never;gvn:true',
               'typeof Map != "undefined"');
   }
 
   factory _LinkedIdentityHashMap.es6() {
     return (_USE_ES6_MAPS && _LinkedIdentityHashMap._supportsEs6Maps)
-        ? new _LinkedIdentityHashMap<K, V>()
-        : new _Es6LinkedIdentityHashMap<K, V>();
+        ? new _Es6LinkedIdentityHashMap<K, V>()
+        : new _LinkedIdentityHashMap<K, V>();
   }
 
   _LinkedIdentityHashMap();
 
   int internalComputeHashCode(var key) {
     // We force the hash codes to be unsigned 30-bit integers to avoid
     // issues with problematic keys like '__proto__'. Another option
     // would be to throw an exception if the hash code isn't a number.
     return JS('int', '# & 0x3ffffff', identityHashCode(key));
   }
@@ skipping 1079 matching lines @@
     } else if (_cell == null) {
       _current = null;
       return false;
     } else {
       _current = _cell._element;
       _cell = _cell._next;
       return true;
     }
   }
 }