Make Fullscreen::fullyExitFullscreen() static

Make Fullscreen::fullyExitFullscreen() static

The implementation may not need the Fullscreen instance for the Document
fullyExitFullscreen() is given, and can avoid creating one for the
top-level Document in case there is no fullscreen element, which is >99%
of time.

BUG=403763
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=180563

[philipj_slow, 2014-08-19 12:33:41]

PTAL and CQ if no nits.

[philipj_slow, 2014-08-19 12:36:28]

I plan to eventually make requestFullscreen() and exitFullscreen() static as
well, since after a spec sync they will return quickly and not need a Fullscreen
instance until actually pushing elements to the fullscreen element stack in a
later callback.

[tkent, 2014-08-19 14:55:01]

The CQ bit was checked by tkent@chromium.org

[tkent, 2014-08-19 14:55:01]

lgtm

[commit-bot: I haz the power, 2014-08-19 14:56:44]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/philipj@opera.com/485953003/1

[commit-bot: I haz the power, 2014-08-19 15:32:19]

Committed patchset #1 (1) as 180563