Fix field-accesses for private fields that were "shadowed" by other private fields.

tests/language/private1.dart

Index: tests/language/private1.dart
diff --git a/tests/language/private1.dart b/tests/language/private1.dart
index 519658ce22159518c02c8c502041b8cffc7f412b..3117b26e574f9b3190300601717c02873fd546ce 100644
--- a/tests/language/private1.dart
+++ b/tests/language/private1.dart
@@ -80,8 +80,10 @@ void testPrivateClasses() {
   expectCatch(() => LibOther3.accessFieldB3(b));
 
   C4 c = new C4();
+  Expect.equals(499, c._field1);
   Expect.equals(499, c_field1a(c));
   Expect.equals(499, c.field1a());
+  Expect.equals(42, c._field2);
   Expect.equals(42, c_field2a(c));
   Expect.equals(42, c.field2a());
   Expect.equals(99, LibOther3.c_field1b(c));