DevTools: Make sure worker instance is not collected.

third_party/WebKit/Source/devtools/front_end/common/Worker.js

 /*
  * Copyright (C) 2014 Google Inc. 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
@@ skipping 31 matching lines @@
 
     var callback;
     /** @type {!Promise<!Worker|!SharedWorker>} */
     this._workerPromise = new Promise(fulfill => callback = fulfill);
 
     /** @type {!Worker|!SharedWorker} */
     var worker;
     var isSharedWorker = !!workerName;
     if (isSharedWorker) {
         worker = new SharedWorker(url, workerName);
-        worker.port.onmessage = onMessage;
+        worker.port.onmessage = onMessage.bind(this);
     } else {
         worker = new Worker(url);
-        worker.onmessage = onMessage;
+        worker.onmessage = onMessage.bind(this);
     }
+    // Hold a reference to worker until the promise is resolved.
+    // Otherwise the worker could be GCed.
+    this._workerProtect = worker;
 
     /**
      * @param {!Event} event
+     * @this {WebInspector.Worker}
      */
     function onMessage(event)
     {
         console.assert(event.data === "workerReady");
         if (isSharedWorker)
             worker.port.onmessage = null;
         else
             worker.onmessage = null;
         callback(worker);
+        this._workerProtect = null;
     }
 }
 
 WebInspector.Worker.prototype = {
     /**
      * @param {*} message
      */
     postMessage: function(message)
     {
         this._workerPromise.then(postToWorker.bind(this));
@@ skipping 59 matching lines @@
          */
         function setOnError(worker)
         {
             if (worker.port)
                 worker.port.onerror = listener;
             else
                 worker.onerror = listener;
         }
     }
 }