use requestAnimationFrame instead of setInterval for animations, when available

[lrbabe]

requestAnimationFrame is a mechanism meant to tell the browser that you wish to perform an animation; this requests that the browser schedule a repaint of the window for the next animation frame.

Full description here:  https://developer.mozilla.org/en/DOM/window.mozRequestAnimationFrame

Benefits:

• let the browser choose the best 'animation tick' rate (instead of our arbitrary 13ms)
• greatly reduce animation CPU usage when switching tab
• helps keep animation synchronized

Full list of claimed benefits here:  http://hacks.mozilla.org/2010/08/more-efficient-javascript-animations-with-mozrequestanimationframe/

Currently supported in Firefox, chromium and Chrome dev channel.

Adding it to jQuery is a minor change (7 lines of Javascript).

[lrbabe]

Oops, this is an enhancement, not a bug sorry. I wish I could fix that by myself.

[lrbabe]

And here is the pull request:  https://github.com/jquery/jquery/pull/216

[snover]

It’s a very good idea, but probably best implemented in the future when production browser actually support (it instead of only pre-release ones since it could be subject to change) :)

[lrbabe]

As I said in the pull request, there's absolutely no need to hurry in merging this patch. I wrote it because I had a good idea of how it good fit into jQuery code and I wanted to do some tests.

Of course, merging it doesn't make sense before Firefox4 and Chrome10 are officially out :-)

[Daniel Lopez]

Firefox 4 and Chrome 10 are officially out :D

[timmywil]

 pull request based off of lrbabe's pull

[john]

Landed.