Remove content::NotificationObserver dependency from most Prefs code.

chrome/browser/net/pref_proxy_config_tracker_impl.cc

 // 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.
 
 #include "chrome/browser/net/pref_proxy_config_tracker_impl.h"
 
 #include "base/bind.h"
 #include "base/values.h"
 #include "chrome/browser/prefs/pref_service.h"
 #include "chrome/browser/prefs/proxy_config_dictionary.h"
@@ skipping 269 matching lines @@
       return true;
     }
     case ProxyPrefs::kModeCount: {
       // Fall through to NOTREACHED().
     }
   }
   NOTREACHED() << "Unknown proxy mode, falling back to system settings.";
   return false;
 }
 
-void PrefProxyConfigTrackerImpl::Observe(
-    int type,
-    const content::NotificationSource& source,
-    const content::NotificationDetails& details) {
+void PrefProxyConfigTrackerImpl::OnPreferenceChanged(
+    PrefServiceBase* service,
+    const std::string& pref_name) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-  if (type == chrome::NOTIFICATION_PREF_CHANGED &&
-      content::Source<PrefService>(source).ptr() == pref_service_) {
+  if (service == pref_service_) {
     net::ProxyConfig new_config;
     ProxyPrefs::ConfigState config_state = ReadPrefConfig(&new_config);
     if (config_state_ != config_state ||
         (config_state_ != ProxyPrefs::CONFIG_UNSET &&
          !pref_config_.Equals(new_config))) {
       config_state_ = config_state;
       if (config_state_ != ProxyPrefs::CONFIG_UNSET)
         pref_config_ = new_config;
       update_pending_ = true;
     }
     if (update_pending_)
       OnProxyConfigChanged(config_state, new_config);
   } else {
-    NOTREACHED() << "Unexpected notification of type " << type;
+    NOTREACHED() << "Unexpected PrefService.";
   }
 }
 
 ProxyPrefs::ConfigState PrefProxyConfigTrackerImpl::ReadPrefConfig(
     net::ProxyConfig* config) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 
   // Clear the configuration and source.
   *config = net::ProxyConfig();
   ProxyPrefs::ConfigState config_state = ProxyPrefs::CONFIG_UNSET;
@@ skipping 14 matching lines @@
         config_state = ProxyPrefs::CONFIG_EXTENSION;
       else
         config_state = ProxyPrefs::CONFIG_OTHER_PRECEDE;
     } else  {
       config_state = ProxyPrefs::CONFIG_FALLBACK;
     }
   }
 
   return config_state;
 }