Revert 148933 &quotUpdateWidget() can fire beforeload event synchron...&quot

      > UpdateWidget() can fire beforeload event synchronously blowing away RenderArena and its associated RenderObjects. In that case, we bail-out and clear m_widgetUpdateSet set.
> 
> BUG=226696
> 
> Review URL: https://codereview.chromium.org/14329005

TBR=inferno@chromium.org

Review URL: https://codereview.chromium.org/16539004

git-svn-id: svn://svn.chromium.org/blink/trunk@152074 bbb929c8-8fbe-4397-9dbb-9b2b20218538