Revert of Properly repaint grid item when z-index changes (https://codereview.chromium.org/246113002/)

Reason for revert:
Depends on https://codereview.chromium.org/203463007/ which broke ChromeOS login
window: https://code.google.com/p/chromium/issues/detail?id=365507

Original issue's description:
> Properly repaint grid item when z-index changes
> 
> Previously z-index changes of static positioned objects are ignored.
> However, z-index is applicable for some static positioned objects,
> such as grid items. Ignoring them makes the object not properly painted
> on z-index change.
> 
> As StyleAdjuster has ensured that z-index is non-auto only if
> applicable, RenderStyle::visualInvalidationDiff() should not check
> again (with inconsistent conditions).
> 
> BUG=234200
> TEST=fast/css-grid/layout/grid-item-z-index-change-repaint.html
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=172168

TBR=jchaffraix@chromium.org,ojan@chromium.org,esprehn@chromium.org,wangxianzhu@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=234200

Review URL: https://codereview.chromium.org/247713004

git-svn-id: svn://svn.chromium.org/blink/trunk@172171 bbb929c8-8fbe-4397-9dbb-9b2b20218538