[d8] Use ValueSerializer for postMessage (instead of ad-hoc serializer)

test/mjsunit/d8-worker.js

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 43 matching lines @@
          break;
        case 5:
          if (m !== 'hi') throw new Error('String');
          break;
        case 6:
          if (JSON.stringify(m) !== '[4,true,\"bye\"]') {
            throw new Error('Array');
          }
          break;
        case 7:
-         if (JSON.stringify(m) !== \"{'a':1,'b':2.5,'c':'three'}\")
-           throw new Error('Object');
+         if (JSON.stringify(m) !== '{"a":1,"b":2.5,"c":"three"}')
+           throw new Error('Object' + JSON.stringify(m));
          break;
        case 8:
          var ab = m;
          var t = new Uint32Array(ab);
          if (ab.byteLength !== 16)
            throw new Error('ArrayBuffer clone byteLength');
          for (var i = 0; i < 4; ++i)
            if (t[i] !== i)
              throw new Error('ArrayBuffer clone value ' + i);
          break;
        case 9:
          var ab = m;
          var t = new Uint32Array(ab);
          if (ab.byteLength !== 32)
            throw new Error('ArrayBuffer transfer byteLength');
          for (var i = 0; i < 8; ++i)
            if (t[i] !== i)
              throw new Error('ArrayBuffer transfer value ' + i);
          break;
      }
      if (c == 10) {
        postMessage('DONE');
      }
    };`;
 
-
 if (this.Worker) {
   function createArrayBuffer(byteLength) {
     var ab = new ArrayBuffer(byteLength);
     var t = new Uint32Array(ab);
     for (var i = 0; i < byteLength / 4; ++i)
       t[i] = i;
     return ab;
   }
 
   var w = new Worker(workerScript);
@@ skipping 26 matching lines @@
 
   w.terminate();
 
 
   // Make sure that the main thread doesn't block forever in getMessage() if
   // the worker dies without posting a message.
   var w2 = new Worker('');
   var msg = w2.getMessage();
   assertEquals(undefined, msg);
 }