Don't use === instead of equality-method call for user class constants.

tests/language/src/CompileTimeConstantNTest.dart

Index: tests/language/src/CompileTimeConstantNTest.dart
diff --git a/tests/language/src/CompileTimeConstantNTest.dart b/tests/language/src/CompileTimeConstantNTest.dart
new file mode 100644
index 0000000000000000000000000000000000000000..af2c5f148a686d49caf7f9dc0a883a2646e3ade0
--- /dev/null
+++ b/tests/language/src/CompileTimeConstantNTest.dart
@@ -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.
+
+class A {
+  const A();
+  operator ==(x) => x == 499;
+}
+
+var a = const A();
+
+main() {
+  if (const A() != 499) Expect.isTrue("const equality failed");
+  Expect.isTrue(a == 499);
+}