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 49 matching lines @@
   };
 
   /* Polyfills */
 
   if (!("runtime" in browser))
     browser.runtime = {};
 
   browser.runtime.sendMessage = (message, responseCallback) =>
   {
     let messageId = ++maxMessageId;
-
     ext.backgroundPage._sendRawMessage({
       type: "message",
       messageId,
       payload: message
     });
 
     let resolvePromise = null;
     let callbackWrapper = event =>
     {
       if (event.data.type == "response" && event.data.messageId == messageId)
       {
         window.removeEventListener("message", callbackWrapper);
         resolvePromise(event.data.payload);
       }
     };
     window.addEventListener("message", callbackWrapper);
     if (responseCallback)
     {
       resolvePromise = responseCallback;
     }
     else
     {
       return new Promise((resolve, reject) =>
       {
         resolvePromise = resolve;
       });
     }
   };
+
+  if (!("tabs" in browser))
+    browser.tabs = new Map([[0, {url: "example.com"}]]);
+
+  browser.tabs.get = (...args) =>
+  {
+    // 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")));
+  };
 }());