Issue 6292 - Make issue reporter compatible with test server

ext/content.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
@@ skipping 83 matching lines @@
         resolvePromise = resolve;
       });
     }
   };
 
   if (!("tabs" in browser))
     browser.tabs = new Map([[0, {url: "example.com"}]]);
 
   browser.tabs.get = (...args) =>
   {
-    let result = Map.prototype.get.apply(browser.tabs, args);
-    return new Promise((resolve, reject) =>
-    {
-      if (result)
-        resolve(result);
-      else
-        reject(new Error("Tab cannot be found"));
-    });
-  }
+    // Extend browser.tabs.get()
+    const result = Map.prototype.get.apply(browser.tabs, args);
+    return (result ? Promise.resolve(result) :
+      Promise.reject(new Error("Tab cannot be found")));
+  };
 }());