Standardize usage of virtual/override/final in extensions/

extensions/browser/updater/null_extension_cache.h

Index: extensions/browser/updater/null_extension_cache.h
diff --git a/extensions/browser/updater/null_extension_cache.h b/extensions/browser/updater/null_extension_cache.h
index c4c9a1bd45e770ce5070d493d435b309e069ddeb..217dbe064a8051f89028c311d8f87b5bae093895 100644
--- a/extensions/browser/updater/null_extension_cache.h
+++ b/extensions/browser/updater/null_extension_cache.h
@@ -13,19 +13,19 @@ namespace extensions {
 class NullExtensionCache : public ExtensionCache {
  public:
   NullExtensionCache();
-  virtual ~NullExtensionCache();
+  ~NullExtensionCache() override;
 
   // ExtensionCache implementation.
-  virtual void Start(const base::Closure& callback) override;
-  virtual void Shutdown(const base::Closure& callback) override;
-  virtual void AllowCaching(const std::string& id) override;
-  virtual bool GetExtension(const std::string& id,
-                            base::FilePath* file_path,
-                            std::string* version) override;
-  virtual void PutExtension(const std::string& id,
-                            const base::FilePath& file_path,
-                            const std::string& version,
-                            const PutExtensionCallback& callback) override;
+  void Start(const base::Closure& callback) override;
+  void Shutdown(const base::Closure& callback) override;
+  void AllowCaching(const std::string& id) override;
+  bool GetExtension(const std::string& id,
+                    base::FilePath* file_path,
+                    std::string* version) override;
+  void PutExtension(const std::string& id,
+                    const base::FilePath& file_path,
+                    const std::string& version,
+                    const PutExtensionCallback& callback) override;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(NullExtensionCache);