Visibility API

Hi webperf folks,

I'd like to check with you if it would make sense to add one more
deliverable to the web performance working group.

There's been a proposal for a Tab Visibility API, which provides a web
developer an API (in Javascript) to find out whether the page is currently
hidden (e.g. not in the foreground tab) vs. visible to the user.
I'm aware of two performance use cases for it:
1) pages that consume a lot of CPU can avoid doing so when the page is not
visible to the user.
2) support html5 <link rel=prefetch> standard (when the browser prefetches a
page, it should let the page know it's not visible).

Below is the discussion on it on whatwg:

http://lists.whatwg.org/htdig.cgi/whatwg-whatwg.org/2010-December/029382.html

I think it makes sense for web performance working group to standardize this
API. Please let me know your thoughts.

Thanks,
Arvind