Implement port equality on SendPortSync

tests/html/js_interop_2_test.dart

Index: tests/html/js_interop_2_test.dart
diff --git a/tests/html/js_interop_2_test.dart b/tests/html/js_interop_2_test.dart
index 7f7550af98f33c9e4cb1f88617cfb137905f3e7e..46a44debbcc9380e250b7ae3f2c3422a26665cae 100644
--- a/tests/html/js_interop_2_test.dart
+++ b/tests/html/js_interop_2_test.dart
@@ -26,6 +26,16 @@ var isolateTest = """
   window.registerPort('test', port.toSendPort());
 """;
 
+var portEqualityTest = """
+  function identity(data) {
+    return data;
+  }
+
+  var port = new ReceivePortSync();
+  port.receive(identity);
+  window.registerPort('identity', port.toSendPort());
+""";
+
 main() {
   useHtmlConfiguration();
 
@@ -39,4 +49,15 @@ main() {
     result = port.callSync('ignore');
     expect(result, isNull);
   });
+
+  test('port-equality', () {
+    injectSource(portEqualityTest);
+
+    SendPortSync port1 = window.lookupPort('identity');
+    SendPortSync port2 = window.lookupPort('identity');
+    expect(port1, equals(port2));
+
+    SendPortSync port3 = port1.callSync(port2);
+    expect(port3, equals(port2));
+  });
 }