chromeos: Delete old, unused contacts code.

chrome/browser/chromeos/contacts/contact_store_observer.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_CHROMEOS_CONTACTS_CONTACT_STORE_OBSERVER_H_
-#define CHROME_BROWSER_CHROMEOS_CONTACTS_CONTACT_STORE_OBSERVER_H_
-
-#include "base/basictypes.h"
-
-namespace contacts {
-
-class ContactStore;
-
-// Interface for observing changes to a ContactStore.
-class ContactStoreObserver {
- public:
-  ContactStoreObserver() {}
-  virtual ~ContactStoreObserver() {}
-
-  // Called when the contacts stored within a ContactStore are updated.
-  virtual void OnContactsUpdated(ContactStore* store) = 0;
-
- private:
-  DISALLOW_COPY_AND_ASSIGN(ContactStoreObserver);
-};
-
-}  // namespace contacts
-
-#endif  // CHROME_BROWSER_CHROMEOS_CONTACTS_CONTACT_STORE_OBSERVER_H_