Remove frog from the repository.

frog/tests/await/doubly_nested_function_test.dart

-// Copyright (c) 2011, 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.
-
-// The next line is used to tell test.dart that this test is run by invoking
-// awaitc.dart and passing this file as an argument (e.g. frog
-// frog/await/awaitc.dart test.dart):
-// VMOptions=frog/await/awaitc.dart
-
-// Await in doubly-nested functions.
-
-#import("await_test_helper.dart");
-
-bool called = false;
-
-main() {
-  f1() {
-    f2() {
-      final x = await futureOf(3);
-      return x + 1;
-    }
-    final x = await f2();
-    return x + 10;
-  }
-  final x = await f1();
-  Expect.equals(14, x);
-}