Issue 3515 - Added polyfill for the fetch() API

lib/polyfills/fetch.js

Index: lib/polyfills/fetch.js
===================================================================
new file mode 100644
--- /dev/null
+++ b/lib/polyfills/fetch.js
@@ -0,0 +1,61 @@
+/*
+ * This file is part of Adblock Plus <https://adblockplus.org/>,
+ * Copyright (C) 2006-2015 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(global)
+{
+  if ("fetch" in global)
+    return;
+
+  function Response(xhr)
+  {
+    this._xhr = xhr;
+  }
+  Response.prototype = {
+    get ok()
+    {
+      return this._xhr.status >= 200 && this._xhr.status <= 299;
+    },
+    text: function()
+    {
+      return Promise.resolve(this._xhr.responseText);
+    }
+  };
+
+  global.fetch = function(url)
+  {
+    return new Promise(function(resolve, reject)
+    {
+      var xhr = new XMLHttpRequest();
+
+      xhr.onload = function()
+      {
+        resolve(new Response(xhr));
+      };
+
+      xhr.onerror = xhr.onabort = function()
+      {
+        reject(new TypeError("Failed to fetch"));
+      };
+
+      xhr.overrideMimeType("text/plain");
+      xhr.open("GET", url);
+      xhr.send();
+    });
+  };
+})(this);