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

shell/src/GcCommand.cpp

 /*
  * 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
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with Adblock Plus.  If not, see <http://www.gnu.org/licenses/>.
  */
 
 #include "GcCommand.h"
 
-GcCommand::GcCommand(AdblockPlus::JsEnginePtr jsEngine)
+GcCommand::GcCommand(AdblockPlus::JsEngine& jsEngine)
   : Command("gc"), jsEngine(jsEngine)
 {
 }
 
 void GcCommand::operator()(const std::string& arguments)
 {
-  jsEngine->Gc();
+  jsEngine.Gc();
 }
 
 std::string GcCommand::GetDescription() const
 {
   return "Initiates a garbage collection";
 }
 
 std::string GcCommand::GetUsage() const
 {
   return name;
 }