Prevent notes polling when there are not notes

CHANGELOG

@@ -8,6 +8,7 @@ v 7.4.0
   - Sort search autocomplete projects by stars count so most popular go first
   - Do not delete tmp/repositories itself during clean-up, only its contents
   - Support for backup uploads to remote storage
+  - Prevent notes polling when there are not notes
 
 v 7.3.1
   - Fix ref parsing in Gitlab::GitAccess

app/assets/javascripts/notes.js.coffee

@@ -6,6 +6,7 @@ class Notes
     @notes_url = gon.relative_url_root + @notes_url if gon.relative_url_root?
     @note_ids = note_ids
     @last_fetched_at = last_fetched_at
+    @noteable_url = document.URL
     @initRefresh()
     @setupMainTargetNoteForm()
     @cleanBinding()
@@ -95,7 +96,8 @@ class Notes
     , 15000
 
   refresh: ->
-    @getContent() unless document.hidden
+    unless document.hidden or (@noteable_url != document.URL)
+      @getContent()
 
   getContent: ->
     $.ajax