DevTools: Get rid of synchronous XHRs in the frontend code

Source/devtools/front_end/profiler/HeapSnapshotProxy.js

 /*
  * Copyright (C) 2011 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 copyrightdd
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 22 matching lines @@
  * @param {function(string, *)} eventHandler
  * @extends {WebInspector.Object}
  */
 WebInspector.HeapSnapshotWorkerProxy = function(eventHandler)
 {
     this._eventHandler = eventHandler;
     this._nextObjectId = 1;
     this._nextCallId = 1;
     this._callbacks = [];
     this._previousCallbacks = [];
-    this._worker = Runtime.startWorker("heap_snapshot_worker");
-    this._worker.onmessage = this._messageReceived.bind(this);
+    this._pendingMessages = [];
+    Runtime.startWorker("heap_snapshot_worker").then(this._init.bind(this)).done();
 }
 
 WebInspector.HeapSnapshotWorkerProxy.prototype = {
     /**
+     * @param {!Worker} worker
+     */
+    _init: function(worker)
+    {
+        this._worker = worker;
+        if (this._disposed) {
+            this.dispose();
+            return;
+        }
+        this._worker.onmessage = this._messageReceived.bind(this);
+        this._handlePendingMessages();
+    },
+
+    _handlePendingMessages: function()
+    {
+        for (var i = 0; i < this._pendingMessages.length; ++i)
+            this._worker.postMessage(this._pendingMessages[i]);
+
+        delete this._pendingMessages;
+    },
+
+    /**
      * @param {number} profileUid
      * @param {function(!WebInspector.HeapSnapshotProxy)} snapshotReceivedCallback
      * @return {!WebInspector.HeapSnapshotLoaderProxy}
      */
     createLoader: function(profileUid, snapshotReceivedCallback)
     {
         var objectId = this._nextObjectId++;
         var proxy = new WebInspector.HeapSnapshotLoaderProxy(this, objectId, profileUid, snapshotReceivedCallback);
         this._postMessage({callId: this._nextCallId++, disposition: "create", objectId: objectId, methodName: "WebInspector.HeapSnapshotLoader"});
         return proxy;
     },
 
     dispose: function()
     {
-        this._worker.terminate();
+        if (this._worker)
+            this._worker.terminate();
+        else
+            this._disposed = true;
         if (this._interval)
             clearInterval(this._interval);
     },
 
     disposeObject: function(objectId)
     {
         this._postMessage({callId: this._nextCallId++, disposition: "dispose", objectId: objectId});
     },
 
     evaluateForTest: function(script, callback)
@@ skipping 90 matching lines @@
             delete this._callbacks[data.callId];
             return;
         }
         if (!this._callbacks[data.callId])
             return;
         var callback = this._callbacks[data.callId];
         delete this._callbacks[data.callId];
         callback(data.result);
     },
 
+    /**
+     * @param {!Object} message
+     */
     _postMessage: function(message)
     {
-        this._worker.postMessage(message);
+        if (this._worker)
+            this._worker.postMessage(message);
+        else
+            this._pendingMessages.push(message);

[pfeldman, 2014/11/07 14:51:17]

You should chain it to the _pendingWorkerPromise instead:

this._pendingWorkerPromise().then(postMessage.bind(this));
function postMessage()
{
    this._worker.postMessage(message);
}

[apavlov, 2014/11/10 07:44:11]

Done.

     },
 
     __proto__: WebInspector.Object.prototype
 }
 
 
 /**
  * @constructor
  * @param {!WebInspector.HeapSnapshotWorkerProxy} worker
  * @param {number} objectId
@@ skipping 251 matching lines @@
          */
         function dataReceived(staticData)
         {
             this._staticData = staticData;
             callback(this);
         }
         this.callMethod(dataReceived.bind(this), "updateStaticData");
     },
 
     /**
-     * @param {!function(!WebInspector.HeapSnapshotCommon.Statistics):void} callback
+     * @param {function(!WebInspector.HeapSnapshotCommon.Statistics):void} callback
      */
     getStatistics: function(callback)
     {
         this.callMethod(callback, "getStatistics");
     },
 
     get totalSize()
     {
         return this._staticData.totalSize;
     },
@@ skipping 68 matching lines @@
      * @param {!WebInspector.HeapSnapshotCommon.ComparatorConfig} comparator
      * @param {function()} callback
      */
     sortAndRewind: function(comparator, callback)
     {
         this.callMethod(callback, "sortAndRewind", comparator);
     },
 
     __proto__: WebInspector.HeapSnapshotProxyObject.prototype
 }