Issue #2230, #3391 - Load filters on "download begin" event

src/plugin/PluginFilter.h

Index: src/plugin/PluginFilter.h
===================================================================
--- a/src/plugin/PluginFilter.h
+++ b/src/plugin/PluginFilter.h
@@ -20,6 +20,7 @@
 
 #include <memory>
 #include <AdblockPlus/FilterEngine.h>
+#include "DetachedInitialization.h"
 
 enum CFilterElementHideAttrPos
 {
@@ -118,6 +119,7 @@
 // ============================================================================
 
 class CPluginFilter
+  : private DetachedInitializer
 {
   // (Tag,Name) -> Filter
   typedef std::multimap<std::pair<std::wstring, std::wstring>, CFilterElementHide> TFilterElementHideTagsNamed;
@@ -126,14 +128,22 @@
   TFilterElementHideTagsNamed m_elementHideTagsId;
   TFilterElementHideTagsNamed m_elementHideTagsClass;
   TFilterElementHideTags m_elementHideTags;
-  void ClearFilters();
+  bool AddFilterElementHide(std::wstring filter);
+  bool LoadHideFilters();
+  const std::wstring domain;
+  InitializerType Initializer() override
+  {
+    return [this] { LoadHideFilters(); };
+  }
 
 public:
-  CPluginFilter();
-  bool LoadHideFilters(std::vector<std::wstring> filters);
-  bool AddFilterElementHide(std::wstring filter);
+  CPluginFilter(const std::wstring& domain)
+    : domain(domain)
+  {
+    SpawnInitializer();
+  }
   bool IsElementHidden(const std::wstring& tag, IHTMLElement* pEl, const std::wstring& domain, const std::wstring& indent) const;
-  HANDLE hideFiltersLoadedEvent;
+  void EnsureInitialized() { DetachedInitializer::EnsureInitialized(); }
 };