Language tests updated to use const instead of final.

tests/language/compile_time_constant8_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<T> {
   const A();
   toString() => "a";
 }
 
-final a = const A<int>();
-final b = const A<double>();
+const a = const A<int>();
+const b = const A<double>();
 
-final list1 = const<int> [1, 2];
-final list2 = const [1, 2];
+const list1 = const<int> [1, 2];
+const list2 = const [1, 2];
 main() {
   Expect.isFalse(a === b);
   Expect.isFalse(list1 === list2);
 }