Warning for multiprofiles sign-in screen extended.

Maximum number of pod rows for sign-in screen is set to 2 when we have warning banner, so that it doesn't break the layout.

BUG=334414

Review URL: https://codereview.chromium.org/138903003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@246039 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 246039