Issue 5028 - Use browser namespace

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 43 matching lines @@
     {
       if (messageQueue)
         messageQueue.push(message);
       else
         backgroundFrame.contentWindow.postMessage(message, "*");
     }
   };
 
   /* Polyfills */
 
-  if (!("runtime" in chrome))
-    chrome.runtime = {};
+  if (!("runtime" in browser))
+    browser.runtime = {};
 
-  chrome.runtime.sendMessage = (message, responseCallback) =>
+  browser.runtime.sendMessage = (message, responseCallback) =>
   {
     let messageId = ++maxMessageId;
 
     ext.backgroundPage._sendRawMessage({
       type: "message",
       messageId,
       payload: message
     });
 
     if (responseCallback)
     {
       let callbackWrapper = event =>
       {
         if (event.data.type == "response" && event.data.messageId == messageId)
         {
           window.removeEventListener("message", callbackWrapper);
           responseCallback(event.data.payload);
         }
       };
 
       window.addEventListener("message", callbackWrapper);
     }
   };
 }());