Remove PrefObserver usage, batch 9.

chrome/browser/safe_browsing/safe_browsing_tab_observer.h

 // 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.
 
 #ifndef CHROME_BROWSER_SAFE_BROWSING_SAFE_BROWSING_TAB_OBSERVER_H_
 #define CHROME_BROWSER_SAFE_BROWSING_SAFE_BROWSING_TAB_OBSERVER_H_
 
 #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 {
 class WebContents;
 }
 
 namespace safe_browsing {
 
 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();
 
  private:
   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
   // safe browsing preference has changed.
   void UpdateSafebrowsingDetectionHost();
 
   // Handles IPCs.
   scoped_ptr<ClientSideDetectionHost> safebrowsing_detection_host_;
 
   // Our owning WebContents.
   content::WebContents* web_contents_;
 
   PrefChangeRegistrar pref_change_registrar_;
 
   DISALLOW_COPY_AND_ASSIGN(SafeBrowsingTabObserver);
 };
 
 }  // namespace safe_browsing
 
 #endif  // CHROME_BROWSER_SAFE_BROWSING_SAFE_BROWSING_TAB_OBSERVER_H_