Standardize usage of virtual/override/final in chrome/browser/download/

chrome/browser/download/download_history.cc

Index: chrome/browser/download/download_history.cc
diff --git a/chrome/browser/download/download_history.cc b/chrome/browser/download/download_history.cc
index 6ca2a734cd7af5d40fdcab1c44c803baaff9f387..9e960824d6ea007b7b4a6d3db06d8268c5263d66 100644
--- a/chrome/browser/download/download_history.cc
+++ b/chrome/browser/download/download_history.cc
@@ -75,8 +75,7 @@ class DownloadHistoryData : public base::SupportsUserData::Data {
     item->SetUserData(kKey, this);
   }
 
-  virtual ~DownloadHistoryData() {
-  }
+  ~DownloadHistoryData() override {}
 
   PersistenceState state() const { return state_; }
   void SetState(PersistenceState s) { state_ = s; }