Fix language/static_final_field2_test to work with tree-shaking in dart2js.

tests/language/static_final_field2_test.dart

Index: tests/language/static_final_field2_test.dart
diff --git a/tests/language/static_final_field2_test.dart b/tests/language/static_final_field2_test.dart
index c80588a5499aaeb8d032c7f250993f1196900aa6..2c550a33f3da2ecd3383df90abaed4b20c3b1e33 100644
--- a/tests/language/static_final_field2_test.dart
+++ b/tests/language/static_final_field2_test.dart
@@ -12,10 +12,11 @@ class B {
   final n;
   static const a;  /// 02: compile-time error
   static const b = 3 + 5;
-  static const c;  /// 02: continued
 }
 
 main() {
   A.x = 2;  /// 01: static type warning, runtime error
   new B();
+  print(B.b);
+  print(B.a);  /// 02: continued
 }