Issue 5450 - don't expose std::shared_ptr<JsEngine>

include/AdblockPlus/Platform.h

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-2017 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 86 matching lines @@
      *
      * @param appInfo Information about the app, if jsEngine is already present
      *        then the value is ignored.
      */
     void SetUpJsEngine(const AppInfo& appInfo = AppInfo());
 
     /**
      * Retrieves the `JsEngine` instance. It calls SetUpJsEngine if JsEngine is
      * not initialized yet.
      */
-    std::shared_ptr<JsEngine> GetJsEngine();
+    JsEngine& GetJsEngine();
 
     /**
      * Ensures that FilterEngine is constructed. Only the first call is effective.
      *
      * @param parameters optional creation parameters.
      * @param onCreated A callback which is called when FilterEngine is ready
      *        for use.
      */
     void CreateFilterEngineAsync(const FilterEngine::CreationParameters& parameters = FilterEngine::CreationParameters(),
       const OnFilterEngineCreatedCallback& onCreated = OnFilterEngineCreatedCallback());
@@ skipping 32 matching lines @@
     FileSystemPtr fileSystem;
     WebRequestPtr webRequest;
     // used for creation and deletion of modules.
     std::mutex modulesMutex;
     std::shared_ptr<JsEngine> jsEngine;
     std::shared_future<FilterEnginePtr> filterEngine;
   };
 }
 
 #endif // ADBLOCK_PLUS_PLATFORM_H