Issue 6622 - Implement $rewrite filter option

lib/requestBlocker.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 171 matching lines @@
 
   if (checkWhitelisted(page, frame, originUrl))
     return;
 
   let type = resourceTypes.get(details.type) || "OTHER";
   let [docDomain, sitekey, specificOnly] = getDocumentInfo(page, frame,
                                                            originUrl);
   let [filter, thirdParty] = matchRequest(url, type, docDomain,
                                           sitekey, specificOnly);
 
+  let result;
+  let rewrittenUrl;
+
+  if (filter instanceof BlockingFilter)
+  {
+    if (filter.rewrite)
+    {
+      rewrittenUrl = filter.rewriteUrl(details.url);
+      // If no rewrite happened (error, different origin), we'll
+      // return undefined in order to avoid an "infinite" loop.
+      if (rewrittenUrl != details.url)
+        result = {redirectUrl: rewrittenUrl};
+    }
+    else
+      result = {cancel: true};
+  }
+
   getRelatedTabIds(details).then(tabIds =>
   {
     logRequest(
       tabIds,
-      {url: details.url, type, docDomain, thirdParty, sitekey, specificOnly},
+      {
+        url: details.url, type, docDomain, thirdParty,
+        sitekey, specificOnly, rewrittenUrl
+      },
       filter
     );
   });
 
-  if (filter instanceof BlockingFilter)
-    return {cancel: true};
+  return result;
 }, {urls: ["<all_urls>"]}, ["blocking"]);
 
 port.on("filters.collapse", (message, sender) =>
 {
   let {page, frame} = sender;
 
   if (checkWhitelisted(page, frame))
     return false;
 
   let blocked = false;
@@ skipping 96 matching lines @@
 }
 
 FilterNotifier.on("subscription.added", onFilterChange);
 FilterNotifier.on("subscription.removed", onFilterChange);
 FilterNotifier.on("subscription.updated", onFilterChange);
 FilterNotifier.on("subscription.disabled", arg => onFilterChange(arg, true));
 FilterNotifier.on("filter.added", onFilterChange);
 FilterNotifier.on("filter.removed", onFilterChange);
 FilterNotifier.on("filter.disabled", arg => onFilterChange(arg, true));
 FilterNotifier.on("load", onFilterChange);