Don`t use references to JsEngine to avoid use-after-free errors,switch to shared_ptr instead

include/AdblockPlus/FilterEngine.h

 #ifndef ADBLOCKPLUS_FILTER_ENGINE_H
 #define ADBLOCKPLUS_FILTER_ENGINE_H
 
 #include <vector>
 #include <map>
 #include <string>
+#include <AdblockPlus/JsEngine.h>
 #include <AdblockPlus/JsValue.h>
 
 #include "tr1_memory.h"
 
 namespace AdblockPlus
 {
-  class JsEngine;
   class FilterEngine;
 
 #if FILTER_ENGINE_STUBS
   class JsObject
 #else
   class JsObject : public JsValue
 #endif
   {
   public:
     std::string GetProperty(const std::string& name, const std::string& defaultValue) const;
@@ skipping 82 matching lines @@
   typedef void (*SubscriptionsCallback)(const std::vector<SubscriptionPtr>&);
 
   class FilterEngine
   {
 #if FILTER_ENGINE_STUBS
     friend class Filter;
     friend class Subscription;
 #endif
 
   public:
-    explicit FilterEngine(JsEngine& jsEngine);
+    explicit FilterEngine(JsEnginePtr jsEngine);
     FilterPtr GetFilter(const std::string& text);
     SubscriptionPtr GetSubscription(const std::string& url);
     const std::vector<FilterPtr> GetListedFilters() const;
     const std::vector<SubscriptionPtr> GetListedSubscriptions() const;
     void FetchAvailableSubscriptions(SubscriptionsCallback callback);
     FilterPtr Matches(const std::string& url,
         const std::string& contentType,
         const std::string& documentUrl);
     std::vector<std::string> GetElementHidingSelectors(const std::string& domain) const;
 
   private:
-    JsEngine& jsEngine;
+    JsEnginePtr jsEngine;
 #if FILTER_ENGINE_STUBS
     std::map<std::string, FilterPtr> knownFilters;
     std::vector<FilterPtr> listedFilters;
     std::map<std::string, SubscriptionPtr> knownSubscriptions;
     std::vector<SubscriptionPtr> listedSubscriptions;
 #endif
   };
 }
 
 #endif