Eliminate BrowserThread usage from PasswordStoreDefault.

chrome/browser/password_manager/password_store_mac.h

 // 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.
 
 #ifndef CHROME_BROWSER_PASSWORD_MANAGER_PASSWORD_STORE_MAC_H_
 #define CHROME_BROWSER_PASSWORD_MANAGER_PASSWORD_STORE_MAC_H_
 
 #include <vector>
 
 #include "base/callback_forward.h"
@@ skipping 26 matching lines @@
       LoginDatabase* login_db);
 
   // Initializes |thread_| and |notification_service_|.
   virtual bool Init() OVERRIDE;
 
   virtual void ShutdownOnUIThread() OVERRIDE;
 
  protected:
   virtual ~PasswordStoreMac();
 
-  virtual scoped_refptr<base::SequencedTaskRunner>
+  virtual scoped_refptr<base::SingleThreadTaskRunner>
       GetBackgroundTaskRunner() OVERRIDE;
 
  private:
   virtual void ReportMetricsImpl() OVERRIDE;
   virtual void AddLoginImpl(const autofill::PasswordForm& form) OVERRIDE;
   virtual void UpdateLoginImpl(
       const autofill::PasswordForm& form) OVERRIDE;
   virtual void RemoveLoginImpl(
       const autofill::PasswordForm& form) OVERRIDE;
   virtual void RemoveLoginsCreatedBetweenImpl(
@@ skipping 43 matching lines @@
   scoped_ptr<base::Thread> thread_;
 
   // Since we aren't running on a well-known thread but still want to send out
   // notifications, we need to run our own service.
   scoped_ptr<content::NotificationService> notification_service_;
 
   DISALLOW_COPY_AND_ASSIGN(PasswordStoreMac);
 };
 
 #endif  // CHROME_BROWSER_PASSWORD_MANAGER_PASSWORD_STORE_MAC_H_