Issue #4692 - Rewrite `SetTimeout` facility to avoid `JsValuePtr` and `JsValueList`

include/AdblockPlus/JsEngine.h

 /*
  * 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 64 matching lines @@
   typedef std::shared_ptr<ScopedV8Isolate> ScopedV8IsolatePtr;
 
   struct ImmediateSingleUseThreadType {}; ///< Marker class for scheduling policy
   extern const ImmediateSingleUseThreadType ImmediateSingleUseThread; ///< Dummy constant for scheduling policy
 
   /**
    * JavaScript engine used by `FilterEngine`, wraps v8.
    */
   class JsEngine : public std::enable_shared_from_this<JsEngine>
   {
-    friend class JsValue;
-    friend class JsContext;
-
   public:
     /**
      * Event callback function.
      */
     typedef std::function<void(JsValueList& params)> EventCallback;
 
     /**
      * Maps events to callback functions.
      */
     typedef std::map<std::string, EventCallback> EventMap;
@@ skipping 168 matching lines @@
     void SetGlobalProperty(const std::string& name, AdblockPlus::JsValuePtr value);
 
     /**
      * Returns a pointer to associated v8::Isolate.
      */
     v8::Isolate* GetIsolate()
     {
       return isolate->Get();
     }
 
-  private:
+  protected:
     explicit JsEngine(const ScopedV8IsolatePtr& isolate);
 
+    /**
+     * Retrieve the global object as a JsValuePtr
+     * 
+     * \par Precondition
+     * - Requires a v8 execution scope already present
+     */
     JsValuePtr GetGlobalObject();
 
     /// Isolate must be disposed only after disposing of all objects which are
     /// using it.
     ScopedV8IsolatePtr isolate;
 
     FileSystemPtr fileSystem;
     WebRequestPtr webRequest;
     LogSystemPtr logSystem;
-    std::unique_ptr<v8::Persistent<v8::Context>> context;
     EventMap eventCallbacks;
 
     // Forward declaration for PImpl idiom
     class SchedulerImpl;
     /**
      * Scheduler for tasks executed under the current engine.
      *
      * \par Invariant
      *   `bool(scheduler)` is always true
      */
     std::unique_ptr<SchedulerImpl> scheduler;
   };
 }
 
 #endif