Handle const loop variable.

tests/language/const_for_in_variable_test.dart

Index: tests/language/const_for_in_variable_test.dart
diff --git a/tests/language/call_function_apply_test.dart b/tests/language/const_for_in_variable_test.dart
similarity index 58%
copy from tests/language/call_function_apply_test.dart
copy to tests/language/const_for_in_variable_test.dart
index 935cfaf832aff599478847534822d651a4ddcd51..a12cd556cd40553244c0dc34efe73cc8e6b4fa03 100644
--- a/tests/language/call_function_apply_test.dart
+++ b/tests/language/const_for_in_variable_test.dart
@@ -2,14 +2,11 @@
 // 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.
 
-import "package:expect/expect.dart";
-
-class A {
-  call({a: 42}) {
-    return 499 + a;
-  }
-}
-
 main() {
-  Expect.equals(497, Function.apply(new A(), [], {#a: -2}));
-}
+  for(
+      const                           /// 01: compile-time error
+      final                           /// 02: ok
+      int x in const [1, 2, 3]) {
+    break;
+  }
+}