Replace deprecated base::NonThreadSafe in chrome/browser/prerender in favor of SequenceChecker.

chrome/browser/prerender/prerender_history.h

 // Copyright (c) 2011 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_PRERENDER_PRERENDER_HISTORY_H_
 #define CHROME_BROWSER_PRERENDER_PRERENDER_HISTORY_H_
 
 #include <stddef.h>
 
 #include <list>
 
 #include "base/macros.h"
-#include "base/threading/non_thread_safe.h"
+#include "base/sequence_checker.h"
 #include "base/time/time.h"
 #include "chrome/browser/prerender/prerender_final_status.h"
 #include "chrome/browser/prerender/prerender_origin.h"
 #include "url/gurl.h"
 
 namespace base {
 class Value;
 }
 
 namespace prerender {
 
 // PrerenderHistory maintains a per-session history of prerendered pages
 // and their final dispositions. It has a fixed maximum capacity, and old
 // items in history will be removed when the capacity is reached.
-class PrerenderHistory : public base::NonThreadSafe {
+class PrerenderHistory {
  public:
   // Entry is an individual entry in the history list. It corresponds to a
   // specific prerendered page.
   struct Entry {
     Entry() : final_status(FINAL_STATUS_MAX), origin(ORIGIN_MAX) {}
 
     Entry(const GURL& url_arg,
           FinalStatus final_status_arg,
           Origin origin_arg,
           base::Time end_time_arg)
@@ skipping 28 matching lines @@
   // Deletes all history entries.
   void Clear();
 
   // Retrieves the entries as a value which can be displayed.
   std::unique_ptr<base::Value> CopyEntriesAsValue() const;
 
  private:
   std::list<Entry> entries_;
   size_t max_items_;
 
+  SEQUENCE_CHECKER(sequence_checker_);
+
   DISALLOW_COPY_AND_ASSIGN(PrerenderHistory);
 };
 
 }  // namespace prerender
 #endif  // CHROME_BROWSER_PRERENDER_PRERENDER_HISTORY_H_