Don't allow to iterate over strings.

tests/language/for_in3_test.dart

Index: tests/language/for_in3_test.dart
diff --git a/tests/language/conflicting_type_variable_and_setter_test.dart b/tests/language/for_in3_test.dart
similarity index 60%
copy from tests/language/conflicting_type_variable_and_setter_test.dart
copy to tests/language/for_in3_test.dart
index 2aca0c32b659b1f1f213c4744ab50c6753befbbc..75ee4852f37512a2f70514a3303ea9a4488ce5e2 100644
--- a/tests/language/conflicting_type_variable_and_setter_test.dart
+++ b/tests/language/for_in3_test.dart
@@ -4,16 +4,11 @@
 
 import "package:expect/expect.dart";
 
-class C<D> {
-  void set D(int value) {
-    field = value;
-  }
-
-  int field;
-}
+// Dart test for testing that strings aren't iterable.
 
 main() {
-  C<int> c = new C<int>();
-  c.D = 1;
-  Expect.equals(c.field, 1);
+  Expect.throws(() {
+    var chars = [];
+    for (var c in "foo") chars.add(c);
+  }, (e) => e is NoSuchMethodError);
 }