This also removes the yellow "warning" background variation, so all
infobars now have the same background color.

BUG=375379
R=dfalcantara@chromium.org

Review URL: https://codereview.chromium.org/346853005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@278877 0039d316-1c4b-4281-b951-d872f2087c98