Use JavaScript runtime semantics when constant folding.

tests/language/compile_time_constant2_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.
 
 const x = 19;
 const y = 3;
+const z = -5;
 const g1 = x + y;
 const g2 = x * y;
 const g3 = x / y;
 const g4 = x ~/ y;
 const g5 = x << y;
 const g6 = x >> y;
-const g7 = ~x;
+const g7 = ~z;
 const g8 = -x;
 const g9 = x < y;
 const g10 = x <= y;
 const g11 = x <= x;
 const g12 = x > y;
 const g13 = x >= y;
 const g14 = x >= x;
 const g15 = x == y;
 const g16 = x == x;
 const g17 = x != y;
 const g18 = x != x;
 const g19 = x | y;
 const g20 = x & y;
 const g21 = x ^ y;
 const g22 = g1 + g2 + g4 + g5 + g6 + g7 + g8;
 const g23 = x % y;
 
 main() {
   Expect.equals(22, g1);
   Expect.equals(57, g2);
   Expect.equals(6.333333333333333333333333333, g3);
   Expect.equals(6, g4);
   Expect.equals(152, g5);
   Expect.equals(2, g6);
-  Expect.equals(-20, g7);
+  Expect.equals(4, g7);
   Expect.equals(-19, g8);
   Expect.equals(false, g9);
   Expect.equals(false, g10);
   Expect.equals(true, g11);
   Expect.equals(true, g12);
   Expect.equals(true, g13);
   Expect.equals(true, g14);
   Expect.equals(false, g15);
   Expect.equals(true, g16);
   Expect.equals(true, g17);
   Expect.equals(false, g18);
   Expect.equals(19, g19);
   Expect.equals(3, g20);
   Expect.equals(16, g21);
-  Expect.equals(200, g22);
+  Expect.equals(224, g22);
   Expect.equals(1, g23);
 }