Issue 3594 - remove circular references JsEngine-JsValue-JsEngine

src/Utils.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
  * 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 <sstream>
 #include <stdexcept>
 
 #ifdef _WIN32
 #include <Windows.h>
 #include <Shlwapi.h>
 #endif
 
 #include "Utils.h"
+#include <AdblockPlus/JsEngine.h>
 
 using namespace AdblockPlus;
 
 std::string Utils::Slurp(std::istream& stream)
 {
   std::stringstream content;
   content << stream.rdbuf();
   return content.str();
 }
 
@@ skipping 60 matching lines @@
     if (FAILED(hr))
     {
       throw std::runtime_error("CanonizeUrl failed\n");
     }
   }
   return canonizedUrl;
 
 }
 #endif
 
+std::shared_ptr<JsEngine> Utils::lockJsEngine(const std::weak_ptr<JsEngine>& jsEngine)
+{
+  auto retValue = jsEngine.lock();
+  if (!retValue)
+    throw AdblockPlus::JsEngine::JsEngineNotAvailableException();
+  return retValue;
+}