Issue 3830 - Add option indicating whether to remove existing filters on raw import

options.js

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-2016 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 573 matching lines @@
           addEnableSubscription(url);
           closeDialog();
           break;
         case "open-dialog":
           openDialog(element.getAttribute("data-dialog"));
           break;
         case "save-custom-filters":
           sendMessageHandleErrors(
           {
             type: "filters.importRaw",
-            text: E("custom-filters-raw").value
+            text: E("custom-filters-raw").value,
+            removeExisting: true
           },
           function()
           {
             E("custom-filters").classList.remove("mode-edit");
           });
           break;
         case "switch-tab":
           document.body.setAttribute("data-tab",
             element.getAttribute("data-tab"));
           break;
@@ skipping 514 matching lines @@
   });
   ext.backgroundPage.sendMessage(
   {
     type: "subscriptions.listen",
     filter: ["added", "disabled", "homepage", "lastDownload", "removed",
         "title"]
   });
 
   window.addEventListener("DOMContentLoaded", onDOMLoaded, false);
 })();