cros: Update "continue" url for samlredirect

Update "continue" url for /samlredirect:
  /o/oauth2/programmatic_auth => /programmatic_auth_chromeos

      to SAML_INTERSTITIAL can sign-in normally.

Bug: b/63865968
Test: Manual. Domains with LoginAuthenticationBehavior policy set
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: I38ca3dcab9c449c8dff29ecf4037dbd397d5b4b4
Reviewed-on: https://chromium-review.googlesource.com/825883Reviewed-by: Achuith Bhandarkar <achuith@chromium.org>
Commit-Queue: Xiyuan Xia <xiyuan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#523981}

chrome/browser/resources/gaia_auth_host/authenticator.js

@@ -336,7 +336,7 @@ cr.define('cr.login', function() {
       url = appendParam(url, 'domain', data.enterpriseEnrollmentDomain);
       url = appendParam(
           url, 'continue',
-          data.gaiaUrl + 'o/oauth2/programmatic_auth?hl=' + data.hl +
+          data.gaiaUrl + 'programmatic_auth_chromeos?hl=' + data.hl +
               '&scope=https%3A%2F%2Fwww.google.com%2Faccounts%2FOAuthLogin&' +
               'client_id=' + encodeURIComponent(data.clientId) +
               '&access_type=offline');