Revert of IFrame Scrollbar needs reconstruction.

Revert of IFrame Scrollbar needs reconstruction. (patchset #3 id:60001 of https://codereview.chromium.org/2314593003/ )

Reason for revert:
virtual/rootlayerscrolls/scrollbars/custom-scrollbar-reconstruction-on-inserting-style-sheet.html fails reliably on Win 10.

https://build.chromium.org/p/chromium.webkit/builders/WebKit%20Win10/builds/14833

Original issue's description:
> IFrame Scrollbar needs reconstruction.
> 
> IFrame Scrollbar needs reconstruction. In the updateWidgetGeometry set
> frameview needs layout if frameview scrollbars needsreconstruction.
> 
> BUG=492785
> 
> Committed: https://crrev.com/5dc5867ab6200abb2f02392a16267ecec62d676e
> Cr-Commit-Position: refs/heads/master@{#418837}

TBR=skobes@chromium.org,majidvp@chromium.org,sataya.m@samsung.com
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=492785

[jbroman, 2016-09-15 14:25:26]

The CQ bit was checked by jbroman@chromium.org

[jbroman, 2016-09-15 14:25:26]

Created Revert of IFrame Scrollbar needs reconstruction.

[jbroman, 2016-09-15 14:25:37]

The CQ bit was unchecked by jbroman@chromium.org

[commit-bot: I haz the power, 2016-09-15 14:25:40]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...