Call el.offsetHeight; to force update of computed style.

Transitions does not work if change is 'auto' -> '0'. As work around code sets
height to offsetHeight before changing height to '0'. However Blink still uses
computed style and does not starts transition. So we have to call el.offsetHeight
to force update computed style.

Removed unused argument from onFadeOutTransitionEnd.

BUG=330604

Review URL: https://codereview.chromium.org/139963002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@245280 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 245280