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

src/plugin/PluginClass.h

Index: src/plugin/PluginClass.h
===================================================================
--- a/src/plugin/PluginClass.h
+++ b/src/plugin/PluginClass.h
@@ -50,8 +50,6 @@
   public ATL::IDispEventImpl<1, CPluginClass, &DIID_DWebBrowserEvents2, &LIBID_SHDocVw, 1, 1>
 {
 
-  friend class CPluginTab;
-
 private:
 
   CPluginTab* m_tab;
@@ -69,6 +67,7 @@
 
   BEGIN_SINK_MAP(CPluginClass)
     SINK_ENTRY_EX(1, DIID_DWebBrowserEvents2, DISPID_BEFORENAVIGATE2, OnBeforeNavigate2)
+    SINK_ENTRY_EX(1, DIID_DWebBrowserEvents2, DISPID_DOWNLOADBEGIN, OnDownloadBegin)
     SINK_ENTRY_EX(1, DIID_DWebBrowserEvents2, DISPID_DOWNLOADCOMPLETE, OnDownloadComplete)
     SINK_ENTRY_EX(1, DIID_DWebBrowserEvents2, DISPID_DOCUMENTCOMPLETE, OnDocumentComplete)
     SINK_ENTRY_EX(1, DIID_DWebBrowserEvents2, DISPID_WINDOWSTATECHANGED, OnWindowStateChanged)
@@ -128,6 +127,7 @@
                                            VARIANT* PostData /**< [in] */,
                                            VARIANT* Headers /**< [in] */,
                                            VARIANT_BOOL* Cancel /* [in, out] */);
+  void STDMETHODCALLTYPE OnDownloadBegin();
   void STDMETHODCALLTYPE OnDownloadComplete();
   void STDMETHODCALLTYPE OnDocumentComplete(IDispatch* frameBrowserDisp, VARIANT* /*urlOrPidl*/);
   void STDMETHODCALLTYPE OnWindowStateChanged(unsigned long flags, unsigned long validFlagsMask);