Better constant fold identity checks. (100 bytes saved on swarm, yeah! :))

tests/language/src/ConstantFoldEqualsTest.dart

Index: tests/language/src/ConstantFoldEqualsTest.dart
===================================================================
--- tests/language/src/ConstantFoldEqualsTest.dart	(revision 0)
+++ tests/language/src/ConstantFoldEqualsTest.dart	(revision 0)
@@ -0,0 +1,15 @@
+// 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.
+
+main() {
+  var a = 'foo';
+  for (int i = 0; i < 10; i++) {
+    if (i == 0) {
+      Expect.isTrue(a === 'foo');
+    } else {
+      Expect.isTrue(a === 2);
+    }
+    a = 2;
+  }
+}