implement mixins in subtype checks, more codegen fixes

lib/runtime/dart/isolate.js

 var isolate;
 (function(exports) {
   'use strict';
   class Capability extends core.Object {
     Capability() {
       return new _isolate_helper.CapabilityImpl();
     }
   }
   class IsolateSpawnException extends core.Object {
     IsolateSpawnException(message) {
@@ skipping 137 matching lines @@
     }
   }
   Isolate.IMMEDIATE = 0;
   Isolate.BEFORE_NEXT_EVENT = 1;
   Isolate.AS_EVENT = 2;
   dart.defineLazyProperties(Isolate, {
     get _currentIsolateCache() {
       return _isolate_helper.IsolateNatives.currentIsolate;
     }
   });
-  class SendPort extends core.Object {
-  }
+  class SendPort extends core.Object {}
   SendPort[dart.implements] = () => [Capability];
   class ReceivePort extends core.Object {
     ReceivePort() {
       return new _isolate_helper.ReceivePortImpl();
     }
     fromRawReceivePort(rawPort) {
       return new _isolate_helper.ReceivePortImpl.fromRawReceivePort(rawPort);
     }
   }
   ReceivePort[dart.implements] = () => [async.Stream];
@@ skipping 39 matching lines @@
   _RemoteStackTrace[dart.implements] = () => [core.StackTrace];
   // Exports:
   exports.Capability = Capability;
   exports.IsolateSpawnException = IsolateSpawnException;
   exports.Isolate = Isolate;
   exports.SendPort = SendPort;
   exports.ReceivePort = ReceivePort;
   exports.RawReceivePort = RawReceivePort;
   exports.RemoteError = RemoteError;
 })(isolate || (isolate = {}));