Switch SupportsUserData uses to use unique_ptr.

components/history/content/browser/web_contents_top_sites_observer.h

 // Copyright 2015 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 COMPONENTS_HISTORY_CONTENT_BROWSER_WEB_CONTENTS_TOP_SITES_OBSERVER_H_
 #define COMPONENTS_HISTORY_CONTENT_BROWSER_WEB_CONTENTS_TOP_SITES_OBSERVER_H_
 
 #include "base/macros.h"
 #include "content/public/browser/web_contents_observer.h"
 #include "content/public/browser/web_contents_user_data.h"
 
 namespace history {
 
 class TopSites;
 
 // WebContentsTopSitesObserver forwards navigation events from
 // content::WebContents to TopSites.
 class WebContentsTopSitesObserver
     : public content::WebContentsObserver,
       public content::WebContentsUserData<WebContentsTopSitesObserver> {
  public:
+  ~WebContentsTopSitesObserver() override;
+
   static void CreateForWebContents(content::WebContents* web_contents,
                                    TopSites* top_sites);
 
  private:
   friend class content::WebContentsUserData<WebContentsTopSitesObserver>;
 
   WebContentsTopSitesObserver(content::WebContents* web_contents,
                               TopSites* top_sites);
-  ~WebContentsTopSitesObserver() override;
 
   // content::WebContentsObserver implementation.
   void NavigationEntryCommitted(
       const content::LoadCommittedDetails& load_details) override;
 
   // Underlying TopSites instance, may be null during testing.
   TopSites* top_sites_;
 
   DISALLOW_COPY_AND_ASSIGN(WebContentsTopSitesObserver);
 };
 
 }  // namespace history
 
 #endif  // COMPONENTS_HISTORY_CONTENT_BROWSER_WEB_CONTENTS_TOP_SITES_OBSERVER_H_