Fix handling of URLs from DHCP server. Remove a DCHECK which proved wrong.

BUG=297810
R=eroman@chromium.org

Review URL: https://codereview.chromium.org/25075002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@226226 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 226226