Move frog/tests/{leg,leg_only,frog_native} to tests/compiler/.

frog/tests/leg_only/to_string_test.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.
-
-class A extends Object {
-}
-
-class Adder {
-  final x;
-  final y;
-  Adder(x, y) : this.x = x, this.y = y;
-  add() => x + y;
-}
-
-test(expected, x) {
-  Expect.equals(expected, x.toString());
-  Expect.equals(expected, new Adder("", x).add());
-}
-
-main() {
-  test("Instance of 'Object'", new Object());
-  test("Instance of 'A'", new A());
-  test("[]", []);
-  test("1", 1);
-}