Moved some MethodMirror properties from embedded API to native calls.

tests/lib/mirrors/method_mirror_test.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.
-
-import "dart:mirrors";
-
-import "../../../pkg/unittest/lib/unittest.dart";
-
-String _symbolToString(Symbol sym) {
-  return MirrorSystem.getName(sym);
-}
-
-doNothing42() {}
-
-main() {
-  // Regression test for http://www.dartbug.com/6335
-  test("NamedMethodName", () {
-    var closureMirror = reflect(doNothing42);
-    expect(_symbolToString(closureMirror.function.simpleName), "doNothing42");
-  });
-}