Made sure FilterEngine instances are always initialized

include/AdblockPlus/JsEngine.h

Index: include/AdblockPlus/JsEngine.h
===================================================================
--- a/include/AdblockPlus/JsEngine.h
+++ b/include/AdblockPlus/JsEngine.h
@@ -13,21 +13,23 @@
  *
  * You should have received a copy of the GNU General Public License
  * along with Adblock Plus.  If not, see <http://www.gnu.org/licenses/>.
  */
 
 #ifndef ADBLOCK_PLUS_JS_ENGINE_H
 #define ADBLOCK_PLUS_JS_ENGINE_H
 
+#include <map>
 #include <stdexcept>
 #include <stdint.h>
 #include <string>
 #include <v8.h>
 #include <AdblockPlus/AppInfo.h>
+#include <AdblockPlus/tr1_functional.h>
 #include <AdblockPlus/LogSystem.h>
 #include <AdblockPlus/FileSystem.h>
 #include <AdblockPlus/JsValue.h>
 #include <AdblockPlus/WebRequest.h>
 
 #include "tr1_memory.h"
 
 namespace AdblockPlus
@@ -42,17 +44,23 @@ namespace AdblockPlus
   class JsEngine;
   typedef std::tr1::shared_ptr<JsEngine> JsEnginePtr;
 
   class JsEngine : public std::tr1::enable_shared_from_this<JsEngine>
   {
     friend class JsValue;
 
   public:
+    typedef std::tr1::function<void()> EventCallback;
+    typedef std::map<std::string, EventCallback> EventMap;
+
     static JsEnginePtr New(const AppInfo& appInfo = AppInfo());
+    void SetEventCallback(const std::string& eventName, EventCallback callback);
+    void RemoveEventCallback(const std::string& eventName);
+    void TriggerEvent(const std::string& eventName);
     JsValuePtr Evaluate(const std::string& source,
         const std::string& filename = "");
     void Gc();
     JsValuePtr NewValue(const std::string& val);
     JsValuePtr NewValue(int64_t val);
     JsValuePtr NewValue(bool val);
     inline JsValuePtr NewValue(const char* val)
     {
@@ -95,12 +103,13 @@ namespace AdblockPlus
   private:
     JsEngine();
 
     FileSystemPtr fileSystem;
     WebRequestPtr webRequest;
     LogSystemPtr logSystem;
     v8::Isolate* isolate;
     v8::Persistent<v8::Context> context;
+    EventMap eventCallbacks;
   };
 }
 
 #endif