autofill: Refactor PersonalDataManager::Observer into its own header file.

chrome/browser/autofill/personal_data_manager_observer.h

+// Copyright (c) 2011 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_AUTOFILL_PERSONAL_DATA_MANAGER_OBSERVER_H_
+#define CHROME_BROWSER_AUTOFILL_PERSONAL_DATA_MANAGER_OBSERVER_H_
+#pragma once
+
+// An interface the PersonalDataManager uses to notify its clients (observers)
+// when it has finished loading personal data from the web database.  Register
+// the observer via PersonalDataManager::SetObserver.
+class PersonalDataManagerObserver {
+ public:
+  // Notifies the observer that the PersonalDataManager changed in some way.
+  virtual void OnPersonalDataChanged() = 0;
+
+ protected:
+  virtual ~PersonalDataManagerObserver() {}
+};
+
+#endif  // CHROME_BROWSER_AUTOFILL_PERSONAL_DATA_MANAGER_OBSERVER_H_