Eliminate BrowserThread usage from PasswordStoreDefault.

chrome/browser/password_manager/password_store_mac.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/password_manager/password_store_mac.h"
 #include "chrome/browser/password_manager/password_store_mac_internal.h"
 
 #include <CoreServices/CoreServices.h>
 #include <set>
 #include <string>
@@ skipping 845 matching lines @@
   return PasswordStore::Init();
 }
 
 void PasswordStoreMac::ShutdownOnUIThread() {
 }
 
 // Mac stores passwords in the system keychain, which can block for an
 // arbitrarily long time (most notably, it can block on user confirmation
 // from a dialog). Run tasks on a dedicated thread to avoid blocking the DB
 // thread.
-scoped_refptr<base::SequencedTaskRunner>
+scoped_refptr<base::SingleThreadTaskRunner>
 PasswordStoreMac::GetBackgroundTaskRunner() {
   return (thread_.get()) ? thread_->message_loop_proxy() : NULL;
 }
 
 void PasswordStoreMac::ReportMetricsImpl() {
   login_metadata_db_->ReportMetrics();
 }
 
 void PasswordStoreMac::AddLoginImpl(const PasswordForm& form) {
   if (AddToKeychainIfNecessary(form)) {
@@ skipping 267 matching lines @@
   owned_keychain_adapter.SetFindsOnlyOwnedItems(true);
   for (std::vector<PasswordForm*>::const_iterator i = forms.begin();
        i != forms.end(); ++i) {
     owned_keychain_adapter.RemovePassword(**i);
   }
 }
 
 void PasswordStoreMac::CreateNotificationService() {
   notification_service_.reset(content::NotificationService::Create());
 }