Check isUserActionElement() instead of separate hover/active/focus checks in supportsStyleSharing()

Check isUserActionElement() instead of separate hover/active/focus checks in supportsStyleSharing()

Since we check all the different states of being a user action element we
should just check the primary bit instead. This function is super hot so
avoiding some branches helps.

This will make us not share for elements in the "active chain", but in the 
common case that's the same as the regular :active elements unless you mutate
the elements in the :active state inside an action (ex. click)

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=171435

[eseidel, 2014-04-14 06:17:06]

What's the microbenchmark you're using to drive this work?  Do you have numbers?
 This one is hard to see that this one branch is quicker than the other two.

[eseidel, 2014-04-14 06:17:44]

lgtm

I can believe that checking one flag is faste rthan checking 3.  Still would be
nice to have numbers.

[esprehn, 2014-04-14 06:45:37]

The CQ bit was checked by esprehn@chromium.org

[commit-bot: I haz the power, 2014-04-14 06:45:48]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/esprehn@chromium.org/236153005/1

[esprehn, 2014-04-14 06:45:57]

On 2014/04/14 06:17:44, eseidel wrote:
> lgtm
> 
> I can believe that checking one flag is faste rthan checking 3.  Still would
be
> nice to have numbers.

I think it makes the code clearer even if it's not faster.

[commit-bot: I haz the power, 2014-04-14 07:51:24]

Change committed as 171435