Several browser tabs: avoiding reload

This is Vaadin’s official solution to multi-tabs and out of sync problem:

If I remove the line ExternalResource(w.getURL()));

in the presented code, the application webpage is not refreshed when opening additional tabs, I don’t get a different url for application tab and I got no “out of sync” errors so far.

I don’t see the relation between having a separate window class (and isolating window-specific state in this class) to the fact of having a different app url for each tab that opens the application.

Is the code above required?

Thanks in advance.