Remove frog from the repository.

frog/tests/await/switch_statement_negative_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
-
-// Illegal to use await in case expressions.
-#import("await_test_helper.dart");
-
-main() {
-  final f = futureOf(1);
-  final x = 3;
-  switch (x) {
-    case await f: return; // illegal to use await here.
-    default: return;
-  }
-}