Issue 5050 - Make legacy extension use WebExtensions I/O

webextension/background.js

Index: webextension/background.js
===================================================================
new file mode 100644
--- /dev/null
+++ b/webextension/background.js
@@ -0,0 +1,41 @@
+/*
+ * 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
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Adblock Plus.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+"use strict";
+
+/* global IO */
+
+let port = browser.runtime.connect();
+
+port.onMessage.addListener(message =>
+{
+  IO[message.method](...message.args).then(result =>
+  {
+    port.postMessage({
+      id: message.id,
+      success: true,
+      result
+    });
+  }).catch(error =>
+  {
+    port.postMessage({
+      id: message.id,
+      success: false,
+      result: String(error)
+    });
+  });
+});