Issue 6908 - Pass updated subscription's old filters as an event argument

lib/filterListener.js

 /*
  * 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
@@ skipping 250 matching lines @@
 
   if (FilterStorage.knownSubscriptions.has(subscription.url))
   {
     if (newValue == false)
       addFilters(subscription.filters);
     else
       subscription.filters.forEach(removeFilter);
   }
 }
 
-function onSubscriptionUpdated(subscription)
+function onSubscriptionUpdated(subscription, oldFilters)
 {
   FilterListener.setDirty(1);
 
   if (!subscription.disabled &&
       FilterStorage.knownSubscriptions.has(subscription.url))
   {
-    subscription.oldFilters.forEach(removeFilter);
+    oldFilters.forEach(removeFilter);
     addFilters(subscription.filters);
   }
 }
 
 function onFilterHitCount(filter, newValue)
 {
   if (newValue == 0)
     FilterListener.setDirty(0);
   else
     FilterListener.setDirty(0.002);
@@ skipping 47 matching lines @@
   {
     if (!subscription.disabled)
       addFilters(subscription.filters);
   }
 }
 
 function onSave()
 {
   isDirty = 0;
 }