Enable "Let me choose what to sync" checkbox in gaia sign in page.

chrome/browser/ui/webui/sync_setup_handler.cc

 // Copyright (c) 2012 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/sync_setup_handler.h"
 
 #include "base/basictypes.h"
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/command_line.h"
@@ skipping 1033 matching lines @@
       } else if (configuring_sync_) {
         ProfileSyncService::SyncEvent(
             ProfileSyncService::CANCEL_DURING_CONFIGURE);
       } else {
         ProfileSyncService::SyncEvent(
             ProfileSyncService::CANCEL_FROM_SIGNON_WITHOUT_AUTH);
       }
     }
 
     // Let the various services know that we're no longer active.
+    if (SyncPromoUI::UseWebBasedSigninFlow())
+      CloseGaiaSigninPage();
+
     GetLoginUIService()->LoginUIClosed(this);
   }
 
   if (sync_service) {
     // Make sure user isn't left half-logged-in (signed in, but without sync
     // started up). If the user hasn't finished setting up sync, then sign out
     // and shut down sync.
     if (!sync_service->HasSyncSetupCompleted()) {
       DVLOG(1) << "Signin aborted by user action";
       sync_service->DisableForUser();
@@ skipping 154 matching lines @@
     if (i != current_profile_index && AreUserNamesEqual(
         cache.GetUserNameOfProfileAtIndex(i), username_utf16)) {
       *error_message = l10n_util::GetStringUTF16(
           IDS_SYNC_USER_NAME_IN_USE_ERROR);
       return false;
     }
   }
 
   return true;
 }