Update {virtual,override} to follow C++11 style in chrome.

chrome/browser/autocomplete/history_url_provider.h

Index: chrome/browser/autocomplete/history_url_provider.h
diff --git a/chrome/browser/autocomplete/history_url_provider.h b/chrome/browser/autocomplete/history_url_provider.h
index 4a43e2d332faee78978a2e5a13b32b727d3c0b18..6a97dff894c6799cbd12817ecf9e62911eb7fa7b 100644
--- a/chrome/browser/autocomplete/history_url_provider.h
+++ b/chrome/browser/autocomplete/history_url_provider.h
@@ -193,11 +193,10 @@ class HistoryURLProvider : public HistoryProvider {
   HistoryURLProvider(AutocompleteProviderListener* listener, Profile* profile);
 
   // HistoryProvider:
-  virtual void Start(const AutocompleteInput& input,
-                     bool minimal_changes,
-                     bool called_due_to_focus) override;
-  virtual void Stop(bool clear_cached_results,
-                    bool due_to_user_inactivity) override;
+  void Start(const AutocompleteInput& input,
+             bool minimal_changes,
+             bool called_due_to_focus) override;
+  void Stop(bool clear_cached_results, bool due_to_user_inactivity) override;
 
   // Returns a match representing a navigation to |destination_url| given user
   // input of |text|.  |trim_http| controls whether the match's |fill_into_edit|
@@ -229,7 +228,7 @@ class HistoryURLProvider : public HistoryProvider {
   };
   class VisitClassifier;
 
-  ~HistoryURLProvider();
+  ~HistoryURLProvider() override;
 
   // Determines the relevance for a match, given its type.  If |match_type| is
   // NORMAL, |match_number| is a number indicating the relevance of the match