Revert "Compute frontend/backend specific constants."

tests/language/const_constructor3_test.dart

-// Copyright (c) 2014, 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 C {
-  final double d;
-  const C(this.d);
-}
-
-class D extends C {
-  const D(var d) : super(d);
-}
-
-const c = const C(0.0); /// 01: ok
-const d = const C(0); /// 02: static type warning, checked mode compile-time error
-const e = const D(0.0); /// 03: ok
-const f = const D(0); /// 04: checked mode compile-time error
-
-main() {
-  print(c); /// 01: continued
-  print(d); /// 02: continued
-  print(e); /// 03: continued
-  print(f); /// 04: continued
-}