Fix equality invocation on native objects

pkg/dev_compiler/tool/input_sdk/private/ddc_runtime/operations.dart

 // Copyright (c) 2015, 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.
 
 /// This library defines runtime operations on objects used by the code
 /// generator.
 part of dart._runtime;
 
 class InvocationImpl extends Invocation {
   final Symbol memberName;
@@ skipping 604 matching lines @@
     return dart.as(object, this);
   };
   $ctor.is = function is_G(object) {
     return dart.is(object, this);
   };
   $ctor._check = function check_G(object) {
     return dart.check(object, this);
   };
 })()''');
 
+// TODO(vsm): Consider optimizing this.  We may be able to statically
+// determine which == operation to invoke given the static types.
 equals(x, y) => JS(
     '',
     '''(() => {
   if ($x == null || $y == null) return $x == $y;
-  let eq = $x['=='];
+  let eq = $x[dartx['==']] || $x['=='];
   return eq ? eq.call($x, $y) : $x === $y;
 })()''');
 
 /// Checks that `x` is not null or undefined. */
 notNull(x) {
   if (x == null) throwNullValueError();
   return x;
 }
 
 ///
@@ skipping 333 matching lines @@
     name = '+' + name;
   }
   return name;
 }
 
 /// Emulates the implicit "loadLibrary" function provided by a deferred library.
 ///
 /// Libraries are not actually deferred in DDC, so this just returns a future
 /// that completes immediately.
 Future loadLibrary() => new Future.value();