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

frog/tests/leg_only/fields_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.
-
-class A {
-  A() {
-  }
-  int x;
-
-  foo() {
-    x = 42;
-    Expect.equals(42, x);
-    x = 0;
-    Expect.equals(0, x);
-  }
-}
-
-class B extends A {
-}
-
-main() {
-  A a = new A();
-  a.foo();
-  Expect.equals(0, a.x);
-  a.x = 4;
-  Expect.equals(4, a.x);
-  a.x += 1;
-  Expect.equals(5, a.x);
-
-  B b = new B();
-  b.foo();
-  Expect.equals(0, b.x);
-}