fix second window not painting on aura while cert dialog is open

In preference to https://codereview.chromium.org/61093002/.

R=sky@chromium.org
BUG=306295

Review URL: https://codereview.chromium.org/59613009

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@233332 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 233332