Remove the last usages of PrefObserver outside of Prefs.

chrome/browser/chromeos/proxy_config_service_impl.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_PROXY_CONFIG_SERVICE_IMPL_H_
 #define CHROME_BROWSER_CHROMEOS_PROXY_CONFIG_SERVICE_IMPL_H_
 
 #include <string>
 #include <vector>
 
 #include "base/basictypes.h"
-#include "base/prefs/public/pref_observer.h"
 #include "base/values.h"
 #include "chrome/browser/api/prefs/pref_member.h"
 #include "chrome/browser/chromeos/cros/network_library.h"
 #include "chrome/browser/net/pref_proxy_config_tracker_impl.h"
 
 namespace chromeos {
 
 // Implementation of proxy config service for chromeos that:
 // - extends PrefProxyConfigTrackerImpl (and so lives and runs entirely on UI
 //   thread) to handle proxy from prefs (via PrefProxyConfigTrackerImpl) and
@@ skipping 272 matching lines @@
   std::vector<base::Closure> callbacks_;
 
   base::WeakPtrFactory<ProxyConfigServiceImpl> pointer_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ProxyConfigServiceImpl);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_PROXY_CONFIG_SERVICE_IMPL_H_