Standardize usage of virtual/override/final in net/

net/disk_cache/blockfile/sparse_control.cc

Index: net/disk_cache/blockfile/sparse_control.cc
diff --git a/net/disk_cache/blockfile/sparse_control.cc b/net/disk_cache/blockfile/sparse_control.cc
index ddb57b624b14e33b04987c7ca7de4d196eac2cdd..30ea836fc7f9d1af45debec8dd245245bdb9e7de 100644
--- a/net/disk_cache/blockfile/sparse_control.cc
+++ b/net/disk_cache/blockfile/sparse_control.cc
@@ -56,7 +56,7 @@ class ChildrenDeleter
   ChildrenDeleter(disk_cache::BackendImpl* backend, const std::string& name)
       : backend_(backend->GetWeakPtr()), name_(name), signature_(0) {}
 
-  virtual void OnFileIOComplete(int bytes_copied) override;
+  void OnFileIOComplete(int bytes_copied) override;
 
   // Two ways of deleting the children: if we have the children map, use Start()
   // directly, otherwise pass the data address to ReadData().
@@ -65,7 +65,7 @@ class ChildrenDeleter
 
  private:
   friend class base::RefCounted<ChildrenDeleter>;
-  virtual ~ChildrenDeleter() {}
+  ~ChildrenDeleter() override {}
 
   void DeleteChildren();