Issue 5013 - Improve some const-correctness

src/FilterEngine.cpp

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-2017 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
@@ skipping 19 matching lines @@
 
 extern std::string jsSources[];
 
 Filter::Filter(JsValue&& value)
     : JsValue(std::move(value))
 {
   if (!IsObject())
     throw std::runtime_error("JavaScript value is not an object");
 }
 
-Filter::Type Filter::GetType() const
+Filter::Type Filter::GetType()
 {
   std::string className = GetClass();
   if (className == "BlockingFilter")
     return TYPE_BLOCKING;
   else if (className == "WhitelistFilter")
     return TYPE_EXCEPTION;
   else if (className == "ElemHideFilter")
     return TYPE_ELEMHIDE;
   else if (className == "ElemHideException")
     return TYPE_ELEMHIDE_EXCEPTION;
@@ skipping 530 matching lines @@
     FilterPtr filter = GetWhitelistingFilter(currentUrl, contentTypeMask, parentUrl);
     if (filter)
     {
       return filter;
     }
     currentUrl = parentUrl;
   }
   while (urlIterator != documentUrls.end());
   return FilterPtr();
 }