Issue #4692 - Rewrite I/O tasks to avoid engine self-reference

src/GlobalJsObject.cpp

 /*
  * 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 129 matching lines @@
     converted.erase(converted.begin());
     jsEngine->TriggerEvent(eventName, converted);
     return v8::Undefined();
   }
 }
 
 JsValuePtr AdblockPlus::GlobalJsObject::Setup(JsEnginePtr jsEngine, const AppInfo& appInfo,
     JsValuePtr obj)
 {
   obj->SetProperty("_triggerEvent", jsEngine->NewCallback(::TriggerEventCallback));
-  obj->SetProperty("_fileSystem",
-      FileSystemJsObject::Setup(jsEngine, jsEngine->NewObject()));
   obj->SetProperty("console",
       ConsoleJsObject::Setup(jsEngine, jsEngine->NewObject()));
   obj->SetProperty("_appInfo",
       AppInfoJsObject::Setup(jsEngine, appInfo, jsEngine->NewObject()));
   return obj;
 }