Standardize usage of virtual/override/final in sync/

sync/test/engine/mock_nudge_handler.h

Index: sync/test/engine/mock_nudge_handler.h
diff --git a/sync/test/engine/mock_nudge_handler.h b/sync/test/engine/mock_nudge_handler.h
index 11f502cabdce74842445d6738c4b2767a9de78ba..477d2bd26fce8d019677ad91e340b2e7fff38087 100644
--- a/sync/test/engine/mock_nudge_handler.h
+++ b/sync/test/engine/mock_nudge_handler.h
@@ -15,11 +15,11 @@ namespace syncer {
 class MockNudgeHandler : public NudgeHandler {
  public:
   MockNudgeHandler();
-  virtual ~MockNudgeHandler();
+  ~MockNudgeHandler() override;
 
-  virtual void NudgeForInitialDownload(syncer::ModelType type) override;
-  virtual void NudgeForCommit(syncer::ModelType type) override;
-  virtual void NudgeForRefresh(syncer::ModelType type) override;
+  void NudgeForInitialDownload(syncer::ModelType type) override;
+  void NudgeForCommit(syncer::ModelType type) override;
+  void NudgeForRefresh(syncer::ModelType type) override;
 
   int GetNumInitialDownloadNudges() const;
   int GetNumCommitNudges() const;