Remove content::NotificationObserver dependency from most Prefs code.

chrome/browser/ui/alternate_error_tab_observer.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/ui/alternate_error_tab_observer.h"
 
 #include "chrome/browser/google/google_util.h"
 #include "chrome/browser/prefs/pref_service.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/common/chrome_notification_types.h"
@@ skipping 38 matching lines @@
   UpdateAlternateErrorPageURL(render_view_host);
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 // content::NotificationObserver overrides
 
 void AlternateErrorPageTabObserver::Observe(
     int type,
     const content::NotificationSource& source,
     const content::NotificationDetails& details) {
-  if (type == chrome::NOTIFICATION_PREF_CHANGED) {
-    DCHECK_EQ(profile_->GetPrefs(), content::Source<PrefService>(source).ptr());
-    DCHECK_EQ(std::string(prefs::kAlternateErrorPagesEnabled),
-              *content::Details<std::string>(details).ptr());
-  } else {
-    DCHECK_EQ(chrome::NOTIFICATION_GOOGLE_URL_UPDATED, type);
-  }
+  DCHECK_EQ(chrome::NOTIFICATION_GOOGLE_URL_UPDATED, type);
   UpdateAlternateErrorPageURL(web_contents()->GetRenderViewHost());
 }
 
+////////////////////////////////////////////////////////////////////////////////
+// PrefObserver overrides
+
+void AlternateErrorPageTabObserver::OnPreferenceChanged(
+    PrefServiceBase* service,
+    const std::string& pref_name) {
+  DCHECK_EQ(profile_->GetPrefs(), service);
+  DCHECK(prefs::kAlternateErrorPagesEnabled == pref_name);
+  UpdateAlternateErrorPageURL(web_contents()->GetRenderViewHost());
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 // Internal helpers
 
 GURL AlternateErrorPageTabObserver::GetAlternateErrorPageURL() const {
   GURL url;
   // Disable alternate error pages when in Incognito mode.
   if (profile_->IsOffTheRecord())
     return url;
 
   if (profile_->GetPrefs()->GetBoolean(prefs::kAlternateErrorPagesEnabled)) {
     url = google_util::LinkDoctorBaseURL();
     if (!url.is_valid())
       return url;
     url = google_util::AppendGoogleLocaleParam(url);
     url = google_util::AppendGoogleTLDParam(profile_, url);
   }
   return url;
 }
 
 void AlternateErrorPageTabObserver::UpdateAlternateErrorPageURL(
     RenderViewHost* rvh) {
   rvh->SetAltErrorPageURL(GetAlternateErrorPageURL());
 }