You should not be using it at all.
It is a Client side operation, not Server side, so it is not even presented to the user until you have finished on the server and sent the page there! So the server side can't use any results the user might want to send it!
Not only that, it's been depreciated for years, and it is just about to be removed completely from Chrome!
https://code.google.com/p/chromium/issues/detail?id=345831[
^]