Added Firefox support

Author: adokseo

background.js

@@ -32,9 +32,14 @@ chrome.runtime.onMessage.addListener(async function (message, sender, sendRespon
     }
 
     if (message.action === 'get-tab-url') {
-        sendResponse({
-            url: new URL(sender.tab.url).hostname,
-            id: sender.tab.id
-        });
+        var response = {
+                url: new URL(sender.url || sender.tab.url).hostname,
+                id: sender.tab.id
+            };
+
+        sendResponse(response);
+        
+        return response;
     }
+
 });

manifest.json

@@ -2,7 +2,7 @@
     "manifest_version": 2,
     "name": "Frame By Frame",
     "description": "__MSG_description__",
-    "version": "2.2.1",
+    "version": "2.2.2",
     "default_locale": "en",
     "icons": {
         "16": "icons/16.png",