Remove content::NotificationObserver dependency from most Prefs code.

chrome/browser/search_engines/template_url_service.h

Index: chrome/browser/search_engines/template_url_service.h
diff --git a/chrome/browser/search_engines/template_url_service.h b/chrome/browser/search_engines/template_url_service.h
index bc62ff53043183133dd897364659a38a86a89d27..510f11c51c00327a2ec5098933650e4b70618bcf 100644
--- a/chrome/browser/search_engines/template_url_service.h
+++ b/chrome/browser/search_engines/template_url_service.h
@@ -15,6 +15,7 @@
 #include "base/memory/scoped_ptr.h"
 #include "base/observer_list.h"
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "chrome/browser/profiles/profile_keyed_service.h"
 #include "chrome/browser/search_engines/template_url_id.h"
 #include "chrome/browser/webdata/web_data_service.h"
@@ -67,6 +68,7 @@ struct URLVisitedDetails;
 class TemplateURLService : public WebDataServiceConsumer,
                            public ProfileKeyedService,
                            public content::NotificationObserver,
+                           public PrefObserver,
                            public syncer::SyncableService {
  public:
   typedef std::map<std::string, std::string> QueryTerms;
@@ -260,10 +262,15 @@ class TemplateURLService : public WebDataServiceConsumer,
   string16 GetKeywordShortName(const string16& keyword,
                                bool* is_extension_keyword);
 
+  // content::NotificationObserver implementation.
   virtual void Observe(int type,
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
+  // PrefObserver implementation.
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
+
   // syncer::SyncableService implementation.
 
   // Returns all syncable TemplateURLs from this model as SyncData. This should