Fix wrong optimization for private fields

tests/language/private1.dart

-// Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
+// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // 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.
 
 // Dart test for testing access to private fields.
 
 main() {
   testPrivateTopLevel();
   testPrivateClasses();
 }
 
@@ skipping 43 matching lines @@
   int _field2;
   C3() : super(), _field2 = 42;
 
   field2a() => _field2;
   field1c() => _field1;
 }
 
 int c_field1a(c) => c._field1;
 int c_field2a(c) => c._field2;
 
+int _field1FromNewC4() => new C4()._field1;
+int _field2FromNewC4() => new C4()._field2;
+
 void testPrivateClasses() {
   _A a = new _A();
   Expect.equals(499, a.fieldA);
   Expect.equals(499, accessFieldA2(a));
   Expect.equals(499, LibOther3.accessFieldA3(a));
 
   var a2 = new AImported();
   Expect.equals(499, a2.getFieldA());
 
   B b = new B();
   Expect.equals(42, b._fieldB);
   Expect.equals(42, accessFieldB2(b));
   expectCatch(() => LibOther3.accessFieldB3(b));
 
   C4 c = new C4();
   Expect.equals(499, c_field1a(c));
   Expect.equals(499, c.field1a());
   Expect.equals(42, c_field2a(c));
   Expect.equals(42, c.field2a());
   Expect.equals(99, LibOther3.c_field1b(c));
   Expect.equals(99, c.field1b());
   Expect.equals(1024, LibOther3.c_field2b(c));
   Expect.equals(1024, c.field2b());
   Expect.equals(499, c.field1c());
   Expect.equals(99, c.field1d());
+  Expect.equals(499, _field1FromNewC4());
+  Expect.equals(42, _field2FromNewC4());
 }