Remove content::NotificationObserver dependency from most Prefs code.

chrome/browser/safe_browsing/safe_browsing_tab_observer.h

Index: chrome/browser/safe_browsing/safe_browsing_tab_observer.h
diff --git a/chrome/browser/safe_browsing/safe_browsing_tab_observer.h b/chrome/browser/safe_browsing/safe_browsing_tab_observer.h
index ec97fee4cca8c037577d538873f444a2b469f724..b41ecb9c19c3a180eb91fce2fa45b72ddff43f99 100644
--- a/chrome/browser/safe_browsing/safe_browsing_tab_observer.h
+++ b/chrome/browser/safe_browsing/safe_browsing_tab_observer.h
@@ -7,7 +7,7 @@
 
 #include "base/memory/scoped_ptr.h"
 #include "base/prefs/public/pref_change_registrar.h"
-#include "content/public/browser/notification_observer.h"
+#include "base/prefs/public/pref_observer.h"
 #include "content/public/browser/web_contents_user_data.h"
 
 namespace content {
@@ -20,7 +20,7 @@ class ClientSideDetectionHost;
 
 // Per-tab class to handle safe-browsing functionality.
 class SafeBrowsingTabObserver
-    : public content::NotificationObserver,
+    : public PrefObserver,
       public content::WebContentsUserData<SafeBrowsingTabObserver> {
  public:
   virtual ~SafeBrowsingTabObserver();
@@ -29,10 +29,9 @@ class SafeBrowsingTabObserver
   explicit SafeBrowsingTabObserver(content::WebContents* web_contents);
   friend class content::WebContentsUserData<SafeBrowsingTabObserver>;
 
-  // content::NotificationObserver overrides:
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details) OVERRIDE;
+  // PrefObserver overrides:
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
 
   // Internal helpers ----------------------------------------------------------