During redirects in the one click sign in flow, check the current URL
instead of original URL to validate gaia http headers.

BUG=307159

Review URL: https://codereview.chromium.org/77343002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@236563 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 236563