Remove frog from the repository.

frog/tests/await/try_catch3_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 within a try-catch block, the awaited future produces the error.
-
-#import("await_test_helper.dart");
-
-errorDuring() {
-  try {
-    final ef = errorOf("my error");
-    final t = await ef;
-    return t;
-  } catch (e) {
-    Expect.equals("my error", e);
-    return 2;
-  }
-}
-
-main() {
-  int t = await errorDuring();
-  Expect.equals(2, t);
-}