Language tests updated to use const instead of final.

tests/language/canonical_const_test.dart

Index: tests/language/canonical_const_test.dart
diff --git a/tests/language/canonical_const_test.dart b/tests/language/canonical_const_test.dart
index 4fd1df8c5b8f836207239d9cbb4453e0cc0a2a4d..c10ce62b81cf025621faf71b4b3040d630ec0c69 100644
--- a/tests/language/canonical_const_test.dart
+++ b/tests/language/canonical_const_test.dart
@@ -4,8 +4,8 @@
 // Check that initializers of static const fields are compile time constants.
 
 class CanonicalConstTest {
-  static final A = const C1();
-  static final B = const C2();
+  static const A = const C1();
+  static const B = const C2();
 
   static testMain() {
     Expect.isTrue(null===null);