Showing unread posts count when new posts appear in the background tab

boards/static/js/thread_update.js

@@ -27,6 +27,7 b' var THREAD_UPDATE_DELAY = 10000;'
 
 var loading = false;
 var lastUpdateTime = null;
+var unreadPosts = 0
 
 function blink(node) {
     var blinkCount = 2;
@@ -99,7 +100,7 b' function updateThread() {'
             updatePostBumpableStatus();
 
             if (data.added.length + data.updated.length > 0) {
-                showNewPostsTitle();
+                showNewPostsTitle(data.added.length);
             }
         })
         .error(function(data) {
@@ -171,15 +172,19 b" var documentOriginalTitle = '';"
 /**
  * Show 'new posts' text in the title if the document is not visible to a user
  */
-function showNewPostsTitle() {
+function showNewPostsTitle(newPostCount) {
     if (document.hidden) {
-        documentOriginalTitle = document.title;
-        document.title = gettext('[new posts]') + ' ' + document.title;
+        if (documentOriginalTitle === '') {
+            documentOriginalTitle = document.title;
+        }
+        unreadPosts = unreadPosts + newPostCount;
+        document.title = '[' + unreadPosts + '] ' + documentOriginalTitle;
 
         document.addEventListener('visibilitychange', function() {
             if (documentOriginalTitle !== '') {
                 document.title = documentOriginalTitle;
                 documentOriginalTitle = '';
+                unreadPosts = 0;
             }
 
             document.removeEventListener('visibilitychange', null);