Remove content::NotificationObserver dependency from most Prefs code.

chrome/browser/translate/translate_manager.h

Index: chrome/browser/translate/translate_manager.h
diff --git a/chrome/browser/translate/translate_manager.h b/chrome/browser/translate/translate_manager.h
index 93eca3a9c3a159878205d70415857cb7e6cb2d2d..eeb5675b6f8f89c82bc303d22ad1659b1eb12e8e 100644
--- a/chrome/browser/translate/translate_manager.h
+++ b/chrome/browser/translate/translate_manager.h
@@ -15,6 +15,7 @@
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "base/time.h"
 #include "chrome/common/translate_errors.h"
 #include "content/public/browser/notification_observer.h"
@@ -41,6 +42,7 @@ class URLFetcher;
 // It is a singleton.
 
 class TranslateManager : public content::NotificationObserver,
+                         public PrefObserver,
                          public net::URLFetcherDelegate {
  public:
   // Returns the singleton instance.
@@ -82,6 +84,10 @@ class TranslateManager : public content::NotificationObserver,
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
+  // PrefObserver implementation:
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
+
   // net::URLFetcherDelegate implementation:
   virtual void OnURLFetchComplete(const net::URLFetcher* source) OVERRIDE;