Issue 3993 - Implement Utils.yield() in a better way (ABP/Firefox part)

lib/utils.js

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-2016 Eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 339 matching lines @@
    * other extension code might execute, the extension might even shut down.
    */
   yield: function()
   {
     let {Prefs} = require("prefs");
     if (Prefs.please_kill_startup_performance)
     {
       this.yield = function() {};
       return;
     }
-    let thread = Services.tm.currentThread;
-    while (thread.processNextEvent(false));
+    return new Promise((resolve, reject) => Utils.runAsync(resolve));
   },
 
   /**
    * Saves sidebar state before detaching/reattaching
    */
   setParams: function(params)
   {
     sidebarParams = params;
   },
 
@@ skipping 394 matching lines @@
     Cu.reportError(e);
     // Expected, ctypes isn't supported in Gecko 1.9.2
     return null;
   }
 });
 
 if ("@mozilla.org/messenger/headerparser;1" in Cc)
   XPCOMUtils.defineLazyServiceGetter(Utils, "headerParser", "@mozilla.org/messenger/headerparser;1", "nsIMsgHeaderParser");
 else
   Utils.headerParser = null;