Reauth causes a MergeSession, so the cookie jar gets re-authed too.

chrome/browser/ui/webui/signin/inline_login_handler_impl.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/ui/webui/signin/inline_login_handler_impl.h"
 
 #include <string>
 
 #include "base/bind.h"
 #include "base/strings/string_number_conversions.h"
@@ skipping 115 matching lines @@
   AccountTrackerService* account_tracker =
       AccountTrackerServiceFactory::GetForProfile(profile_);
   std::string account_id =
       account_tracker->PickAccountIdForAccount(gaia_id_, email_);
 
   // Prime the account tracker with this combination of gaia id/display email.
   account_tracker->SeedAccountInfo(gaia_id_, email_);
 
   signin_metrics::Source source = signin::GetSourceForPromoURL(current_url_);
 
-  std::string primary_email =
-      SigninManagerFactory::GetForProfile(profile_)->GetAuthenticatedUsername();
+  SigninManager* signin_manager = SigninManagerFactory::GetForProfile(profile_);
+  std::string primary_email = signin_manager->GetAuthenticatedUsername();
   if (gaia::AreEmailsSame(email_, primary_email) &&
       source == signin_metrics::SOURCE_REAUTH &&
       switches::IsNewProfileManagement() &&
       !password_.empty() &&
       profiles::IsLockAvailable(profile_)) {
     LocalAuth::SetLocalAuthCredentials(profile_, password_);
   }
 
   if (source == signin_metrics::SOURCE_AVATAR_BUBBLE_ADD_ACCOUNT ||
       source == signin_metrics::SOURCE_REAUTH) {
     ProfileOAuth2TokenServiceFactory::GetForProfile(profile_)->
         UpdateCredentials(account_id, result.refresh_token);
 
     if (signin::IsAutoCloseEnabledInURL(current_url_)) {
       // Close the gaia sign in tab via a task to make sure we aren't in the
       // middle of any webui handler code.
       base::MessageLoop::current()->PostTask(
           FROM_HERE,
           base::Bind(&InlineLoginHandlerImpl::CloseTab,
           handler_,
           signin::ShouldShowAccountManagement(current_url_)));
     }
+
+    if (source == signin_metrics::SOURCE_REAUTH)
+      signin_manager->MergeSigninCredentialIntoCookieJar();
   } else {
     ProfileSyncService* sync_service =
         ProfileSyncServiceFactory::GetForProfile(profile_);
     SigninErrorController* error_controller =
         SigninErrorControllerFactory::GetForProfile(profile_);
 
     bool is_new_avatar_menu = switches::IsNewAvatarMenu();
 
     OneClickSigninSyncStarter::StartSyncMode start_mode;
     if (source == signin_metrics::SOURCE_SETTINGS || choose_what_to_sync_) {
@@ skipping 287 matching lines @@
       }
     }
 
     if (show_account_management) {
       browser->window()->ShowAvatarBubbleFromAvatarButton(
             BrowserWindow::AVATAR_BUBBLE_MODE_ACCOUNT_MANAGEMENT,
             signin::ManageAccountsParams());
     }
   }
 }