Reapply change to update dart2js operator equals semantics to follow

tests/language/operator5_test.dart

Index: tests/language/operator5_test.dart
diff --git a/tests/language/operator5_test.dart b/tests/language/operator5_test.dart
index 87c86fbb8c04163e1256ed1fc1fa47e8f467950c..52c9bcb9894e0c0fc20a29483499c2a5c3edf8e5 100644
--- a/tests/language/operator5_test.dart
+++ b/tests/language/operator5_test.dart
@@ -19,14 +19,6 @@ equals(a) {
   }
 }
 
-equalsNull(a) {
-  try {
-    Expect.equals(1, a == null);
-  } catch(TypeError e) {
-    // In checked mode the test doesn't do anything.
-  }
-}
-
 less(a) {
   try {
     Expect.equals(null, a < a);