Issue 5258 - Implement Filter::As<>() method to make working with filters easier from C++ code

compiled/filter/Filter.h

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-present eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with Adblock Plus.  If not, see <http://www.gnu.org/licenses/>.
  */
 
 #pragma once
 
-#include <type_traits>
 #include <vector>
 
 #include "../String.h"
 #include "../intrusive_ptr.h"
 #include "../debug.h"
 #include "../bindings/runtime.h"
 
 class Filter : public ref_counted
 {
 protected:
@@ skipping 22 matching lines @@
 
   const String& BINDINGS_EXPORTED GetText() const
   {
     return mText;
   }
 
   OwnedString BINDINGS_EXPORTED Serialize() const;
 
   static Filter* BINDINGS_EXPORTED FromText(DependentString& text);
 
-  template<typename T,
-    typename std::enable_if<std::is_base_of<Filter, T>::value>::type* = nullptr>
+  template<typename T>
   T* As()
   {
     if ((mType & T::classType) != T::classType)
       return nullptr;
 
     return static_cast<T*>(this);
   }
 
-  template<typename T,
-    typename std::enable_if<std::is_base_of<Filter, T>::value>::type* = nullptr>
+  template<typename T>
   const T* As() const
   {
     if ((mType & T::classType) != T::classType)
       return nullptr;
 
     return static_cast<const T*>(this);
   }
 };
 
 typedef intrusive_ptr<Filter> FilterPtr;