Issue 6424 - Use internal symbol in ext namespace

base.js

Index: base.js
===================================================================
new file mode 100644
--- /dev/null
+++ b/base.js
@@ -0,0 +1,49 @@
+/*
+ * 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
+ * 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";
+
+{
+  const {create, defineProperty, getPrototypeOf, keys} = Object;
+
+  const {hasOwnProperty} = Object.prototype;
+  const {bind} = Function.prototype;
+
+  window.defineNamespace = (object, namespace) =>
+  {
+    let prototype = null;
+
+    // If the object has a prototype and the prototype has the same namespace,
+    // copy over all the functions in that namespace to our prototype,
+    // additionally binding them to the object.
+    let objectPrototype = getPrototypeOf(object);
+    if (objectPrototype && hasOwnProperty.call(objectPrototype, namespace))
+    {
+      prototype = create(null);
+
+      let objectPrototypeNamespace = objectPrototype[namespace];
+      for (let key of keys(objectPrototypeNamespace))
+      {
+        let value = objectPrototypeNamespace[key];
+        if (typeof value == "function")
+          prototype[key] = bind.call(value, object);
+      }
+    }
+
+    return defineProperty(object, namespace, {value: create(prototype)});
+  };
+}