Remove PrefObserver usage, batch 9.

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 b41ecb9c19c3a180eb91fce2fa45b72ddff43f99..45e7be40a20bedc37ab80a8bb5b254b3e2a8cc43 100644
--- a/chrome/browser/safe_browsing/safe_browsing_tab_observer.h
+++ b/chrome/browser/safe_browsing/safe_browsing_tab_observer.h
@@ -7,7 +7,6 @@
 
 #include "base/memory/scoped_ptr.h"
 #include "base/prefs/public/pref_change_registrar.h"
-#include "base/prefs/public/pref_observer.h"
 #include "content/public/browser/web_contents_user_data.h"
 
 namespace content {
@@ -20,8 +19,7 @@ class ClientSideDetectionHost;
 
 // Per-tab class to handle safe-browsing functionality.
 class SafeBrowsingTabObserver
-    : public PrefObserver,
-      public content::WebContentsUserData<SafeBrowsingTabObserver> {
+    : public content::WebContentsUserData<SafeBrowsingTabObserver> {
  public:
   virtual ~SafeBrowsingTabObserver();
 
@@ -29,10 +27,6 @@ class SafeBrowsingTabObserver
   explicit SafeBrowsingTabObserver(content::WebContents* web_contents);
   friend class content::WebContentsUserData<SafeBrowsingTabObserver>;
 
-  // PrefObserver overrides:
-  virtual void OnPreferenceChanged(PrefServiceBase* service,
-                                   const std::string& pref_name) OVERRIDE;
-
   // Internal helpers ----------------------------------------------------------
 
   // Create or destroy SafebrowsingDetectionHost as needed if the user's