Remove content::NotificationObserver dependency from most Prefs code.

chrome/browser/printing/cloud_print/cloud_print_proxy_service.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/printing/cloud_print/cloud_print_proxy_service.h"
 
 #include <stack>
 #include <vector>
 
 #include "base/bind.h"
@@ skipping 189 matching lines @@
     }
   }
   return true;
 }
 
 void CloudPrintProxyService::OnCloudPrintSetupClosed() {
   MessageLoop::current()->PostTask(
       FROM_HERE, base::Bind(&browser::EndKeepAlive));
 }
 
-void CloudPrintProxyService::Observe(
-    int type,
-    const content::NotificationSource& source,
-    const content::NotificationDetails& details) {
-  DCHECK_EQ(chrome::NOTIFICATION_PREF_CHANGED, type);
+void CloudPrintProxyService::OnPreferenceChanged(PrefServiceBase* service,
+                                                 const std::string& pref_name) {
   ApplyCloudPrintConnectorPolicy();
 }
 
 void CloudPrintProxyService::RefreshCloudPrintProxyStatus() {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
   ServiceProcessControl* process_control = GetServiceProcessControl();
   DCHECK(process_control->IsConnected());
   ServiceProcessControl::CloudPrintProxyInfoHandler callback =
        base::Bind(&CloudPrintProxyService::ProxyInfoCallback,
                   base::Unretained(this));
@@ skipping 44 matching lines @@
 }
 
 bool CloudPrintProxyService::InvokeServiceTask(const base::Closure& task) {
   GetServiceProcessControl()->Launch(task, base::Closure());
   return true;
 }
 
 ServiceProcessControl* CloudPrintProxyService::GetServiceProcessControl() {
   return ServiceProcessControl::GetInstance();
 }