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

chrome/browser/prerender/prerender_history.h

Index: chrome/browser/prerender/prerender_history.h
diff --git a/chrome/browser/prerender/prerender_history.h b/chrome/browser/prerender/prerender_history.h
index 228687a1c5fdbf3ad6fe381e04f5a4432f748d40..a5cc6ffa0f7cca667ec4c93b4cf9154f1d576db1 100644
--- a/chrome/browser/prerender/prerender_history.h
+++ b/chrome/browser/prerender/prerender_history.h
@@ -10,7 +10,7 @@
 #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"
@@ -25,7 +25,7 @@ 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.
@@ -74,6 +74,8 @@ class PrerenderHistory : public base::NonThreadSafe {
   std::list<Entry> entries_;
   size_t max_items_;
 
+  SEQUENCE_CHECKER(sequence_checker_);
+
   DISALLOW_COPY_AND_ASSIGN(PrerenderHistory);
 };