Revert of Revert of Move preferred scrollbar style preference change listening from renderer to browser, 3 of 3. (https://codereview.chromium.org/147193002/)

Reason for revert:
Fixed in Chromium with https://codereview.chromium.org/145013018

Original issue's description:
> Revert of Move preferred scrollbar style preference change listening from renderer to browser, 3 of 3. (https://codereview.chromium.org/136333009/)
> 
> Reason for revert:
> This seems to be causing a mac_rel failure and is blocking blink roll.
> 
> see here: http://build.chromium.org/p/tryserver.chromium/builders/mac_rel/builds/215993/steps/content_browsertests/logs/stdio
> 
> 
> Original issue's description:
> > Move preferred scrollbar style preference change listening from renderer to browser, 3 of 3.
> > 
> > This removes the preferred style listener from Blink, now that the browser
> > sends the value when it changes over IPC.
> > 
> > BUG=306348
> > 
> > Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=165714
> 
> TBR=jamesr@chromium.org,thakis@chromium.org,rsesek@chromium.org
> NOTREECHECKS=true
> NOTRY=true
> BUG=306348
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=165774

TBR=jamesr@chromium.org,thakis@chromium.org,hclam@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=306348

Review URL: https://codereview.chromium.org/144363003

git-svn-id: svn://svn.chromium.org/blink/trunk@165857 bbb929c8-8fbe-4397-9dbb-9b2b20218538