Issue 5347 - Check for contextMenus API support

lib/filterComposer.js

 /*
  * 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 166 matching lines @@
 function updateContextMenu(page, filter)
 {
   page.contextMenus.remove(contextMenuItem);
 
   if (typeof filter == "undefined")
     filter = checkWhitelisted(page);
   if (!filter && Prefs.shouldShowBlockElementMenu && readyPages.has(page))
     page.contextMenus.create(contextMenuItem);
 }
 
-FilterNotifier.on("page.WhitelistingStateRevalidate", updateContextMenu);
+if ("contextMenus" in chrome)
+{
+  FilterNotifier.on("page.WhitelistingStateRevalidate", updateContextMenu);
 
-Prefs.on("shouldShowBlockElementMenu", () =>
-{
-  ext.pages.query({}, pages =>
+  Prefs.on("shouldShowBlockElementMenu", () =>
   {
-    for (let page of pages)
-      updateContextMenu(page);
+    ext.pages.query({}, pages =>
+    {
+      for (let page of pages)
+        updateContextMenu(page);
+    });
   });
-});
+}
 
 port.on("composer.ready", (message, sender) =>
 {
   readyPages.set(sender.page, null);
-  updateContextMenu(sender.page);
+
+  if ("contextMenus" in chrome)
+    updateContextMenu(sender.page);
 });
 
 port.on("composer.openDialog", (message, sender) =>
 {
   return new Promise(resolve =>
   {
     ext.windows.create({
       url: ext.getURL("composer.html"),
       left: 50,
       top: 50,
@@ skipping 39 matching lines @@
 
 port.on("composer.quoteCSS", (message, sender) =>
 {
   return quoteCSS(message.CSS);
 });
 
 ext.pages.onLoading.addListener(page =>
 {
   page.sendMessage({type: "composer.content.finished"});
 });