Remove private class helping the parser to construct literal lists and maps.

runtime/lib/map_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 class _HashMapImpl<K, V> {
+  // Factory constructing a Map from a parser generated Map literal.
+  // [elements] contains n key-value pairs.
+  // The keys are at position 2*n and are already type checked by the parser
+  // in checked mode.
+  // The values are at position 2*n+1 and are not yet type checked.
+  factory Map._fromLiteral(List elements) {
+    var map = new LinkedHashMap<String, V>();
+    var len = elements.length;
+    for (int i = 1; i < len; i += 2) {
+      map[elements[i - 1]] = elements[i];
+    }
+    return map;
+  }
+}