Made sure FilterEngine instances are always initialized

src/JsEngine.cpp

Index: src/JsEngine.cpp
===================================================================
--- a/src/JsEngine.cpp
+++ b/src/JsEngine.cpp
@@ -88,16 +88,30 @@ AdblockPlus::JsValuePtr AdblockPlus::JsE
   const v8::TryCatch tryCatch;
   const v8::Handle<v8::Script> script = CompileScript(source, filename);
   CheckTryCatch(tryCatch);
   v8::Local<v8::Value> result = script->Run();
   CheckTryCatch(tryCatch);
   return JsValuePtr(new JsValue(shared_from_this(), result));
 }
 
+void AdblockPlus::JsEngine::SetInitCallback(AdblockPlus::JsEngine::InitCallback callback)
+{
+  initCallback = callback;
+}
+
+void AdblockPlus::JsEngine::InitDone()
+{
+  // Zero out callback immediately to prevent reentrance
+  InitCallback callback = initCallback;
+  initCallback = 0;
+  if (callback)
+    callback();
+}
+
 void AdblockPlus::JsEngine::Gc()
 {
   while (!v8::V8::IdleNotification());
 }
 
 AdblockPlus::JsValuePtr AdblockPlus::JsEngine::NewValue(const std::string& val)
 {
   const Context context(shared_from_this());