Revert of Always attach overflow controls to the right parent (https://codereview.chromium.org/266003004/)

Reason for revert:
The expectation from the patch is against the actual result. Looks like the patch doesn't work as expected. http://test-results.appspot.com/dashboards/flakiness_dashboard.html#group=%40ToT%20Blink&showExpectations=true&showLargeExpectations=true&tests=fixed-body-background-positioned.html

Original issue's description:
> Always attach overflow controls to the right parent
> 
> Overflow controls like scrollbars and scroll corners can either be
> parented by root transform layer (which optionally might exist) or the
> overflow controls host layer (if the root transform layer does not).
> 
> Previously, overflow controls were parented to the first control parent
> that they were attached to, and if the root transform layer got created,
> they wouldn't be reparented to it.  This leads to raciness between
> adding scrollbars and adding the root transform layer.
> 
> To fix this, always reparent these controls if the controlsParent has
> changed.
> 
> BUG=361729
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=173263

TBR=vollick@chromium.org,ojan@chromium.org,abarth@chromium.org,enne@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=361729

Review URL: https://codereview.chromium.org/262203002

git-svn-id: svn://svn.chromium.org/blink/trunk@173288 bbb929c8-8fbe-4397-9dbb-9b2b20218538