Issue 6539, 6782 - Implement support for snippets

lib/contentFiltering.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 180 matching lines @@
       // Sometimes a frame is added and removed very quickly, in such cases we
       // simply ignore the error.
       if (error.message == "The frame was removed.")
         return;
 
       throw error;
     });
   }
   catch (error)
   {
+    // See the comment in the catch block associated with the call to
+    // tabs.insertCSS for why we catch and ignore any errors here.
   }
 }
 
 port.on("content.applyFilters", (message, sender) =>
 {
   let selectors = [];
   let emulatedPatterns = [];
   let trace = HitLogger.hasListener(sender.page.id);
   let inline = !userStyleSheetsSupported;
 
@@ skipping 48 matching lines @@
   updateFrameStyles(sender.page.id, sender.frame.id, message.selectors,
                     message.groupName, message.appendOnly);
 });
 
 fetch(browser.extension.getURL("/snippets.js"), {cache: "no-cache"})
 .then(response => response.ok ? response.text() : "")
 .then(text =>
 {
   snippetsLibrarySource = text;
 });