Issue 5028 - Use browser namespace

polyfill.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
  * 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";
 
-(function()
+// Unlike Firefox and Microsoft Edge, Chrome doesn't have a "browser" object,
+// but provides the extension API through the "chrome" namespace
+// (non-standard).
+if (typeof browser == "undefined")
+  window.browser = chrome;
+
+// Workaround since HTMLCollection, NodeList, StyleSheetList, and CSSRuleList
+// didn't have iterator support before Chrome 51.
+// https://bugs.chromium.org/p/chromium/issues/detail?id=401699
+for (let object of [HTMLCollection, NodeList, StyleSheetList, CSSRuleList])
 {
-  // On Edge, the extension APIs are in the "browser" namespace, whereas on
-  // both Firefox and Chrome they're in the "chrome" namespace. Firefox has a
-  // "browser" namespace too, but it is slightly incompatible in that the
-  // implementation uses promises as a fallback in the absence of a callback
-  // parameter. Edge sometimes has a "chrome" namespace, but with no extension
-  // APIs.
-  //
-  // In order to make the same code run on all three platforms, we simply look
-  // for a "chrome" namespace with the extension APIs and assign it to the
-  // "browser" namespace.
-  if (typeof chrome != "undefined" && "extension" in chrome)
-    window.browser = chrome;
-
-  // Workaround since HTMLCollection, NodeList, StyleSheet and
-  // CSSRuleList didn't have iterator support before Chrome 51.
-  // https://bugs.chromium.org/p/chromium/issues/detail?id=401699
-  let arrayIterator = Array.prototype[Symbol.iterator];
-  if (!(Symbol.iterator in HTMLCollection.prototype))
-    HTMLCollection.prototype[Symbol.iterator] = arrayIterator;
-  if (!(Symbol.iterator in NodeList.prototype))
-    NodeList.prototype[Symbol.iterator] = arrayIterator;
-  if (!(Symbol.iterator in StyleSheetList.prototype))
-    StyleSheetList.prototype[Symbol.iterator] = arrayIterator;
-  if (!(Symbol.iterator in CSSRuleList.prototype))
-    CSSRuleList.prototype[Symbol.iterator] = arrayIterator;
-}());
+  if (!(Symbol.iterator in object.prototype))
+    object.prototype[Symbol.iterator] = Array.prototype[Symbol.iterator];
+}