Remove content::NotificationObserver dependency from most Prefs code.

chrome/browser/profiles/gaia_info_update_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/profiles/gaia_info_update_service.h"
 
 #include "base/command_line.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/prefs/pref_service.h"
 #include "chrome/browser/profiles/profile.h"
@@ skipping 146 matching lines @@
     ProfileDownloader* downloader) {
   profile_image_downloader_.reset();
 
   // Save the last updated time.
   last_updated_ = base::Time::Now();
   profile_->GetPrefs()->SetInt64(prefs::kProfileGAIAInfoUpdateTime,
                                  last_updated_.ToInternalValue());
   ScheduleNextUpdate();
 }
 
-void GAIAInfoUpdateService::Observe(
-    int type,
-    const content::NotificationSource& source,
-    const content::NotificationDetails& details) {
-  if (type == chrome::NOTIFICATION_PREF_CHANGED) {
-    std::string* name = content::Details<std::string>(details).ptr();
-    if (prefs::kGoogleServicesUsername == *name)
-      OnUsernameChanged();
-  } else {
-    NOTREACHED();
-  }
+void GAIAInfoUpdateService::OnPreferenceChanged(PrefServiceBase* service,
+                                                const std::string& pref_name) {
+  if (prefs::kGoogleServicesUsername == pref_name)
+    OnUsernameChanged();
 }
 
 void GAIAInfoUpdateService::OnUsernameChanged() {
   ProfileInfoCache& cache =
       g_browser_process->profile_manager()->GetProfileInfoCache();
   size_t profile_index = cache.GetIndexOfProfileWithPath(profile_->GetPath());
   if (profile_index == std::string::npos)
     return;
 
   std::string username = profile_->GetPrefs()->GetString(
@@ skipping 23 matching lines @@
   const base::TimeDelta update_delta = base::Time::Now() - last_updated_;
 
   base::TimeDelta delta;
   if (update_delta < base::TimeDelta() || update_delta > desired_delta)
     delta = base::TimeDelta::FromSeconds(kMinUpdateIntervalSeconds);
   else
     delta = desired_delta - update_delta;
 
   timer_.Start(FROM_HERE, delta, this, &GAIAInfoUpdateService::Update);
 }