Use signature inheritance when method types are unchanged

lib/runtime/dart/_isolate_helper.js

Index: lib/runtime/dart/_isolate_helper.js
diff --git a/lib/runtime/dart/_isolate_helper.js b/lib/runtime/dart/_isolate_helper.js
index d2ea54a36fdc4d74d3632333cc5bf2d9cd45da89..b755db7f88d64ae799dd211fc3db416f0b13678e 100644
--- a/lib/runtime/dart/_isolate_helper.js
+++ b/lib/runtime/dart/_isolate_helper.js
@@ -1287,10 +1287,7 @@ var async = dart.import(async);
   }
   _NativeJsSendPort[dart.implements] = () => [isolate.SendPort];
   dart.setSignature(_NativeJsSendPort, {
-    methods: () => ({
-      send: dart.functionType(dart.void, [dart.dynamic]),
-      '==': dart.functionType(core.bool, [dart.dynamic])
-    })
+    methods: () => ({send: dart.functionType(dart.void, [dart.dynamic])})
   });
   class _WorkerSendPort extends _BaseSendPort {
     _WorkerSendPort(workerId, isolateId, receivePortId) {
@@ -1318,10 +1315,7 @@ var async = dart.import(async);
   }
   _WorkerSendPort[dart.implements] = () => [isolate.SendPort];
   dart.setSignature(_WorkerSendPort, {
-    methods: () => ({
-      send: dart.functionType(dart.void, [dart.dynamic]),
-      '==': dart.functionType(core.bool, [dart.dynamic])
-    })
+    methods: () => ({send: dart.functionType(dart.void, [dart.dynamic])})
   });
   let _handler = Symbol('_handler');
   class RawReceivePortImpl extends core.Object {