Standardize usage of virtual/override/final in base/

base/threading/thread_local_storage_unittest.cc

Index: base/threading/thread_local_storage_unittest.cc
diff --git a/base/threading/thread_local_storage_unittest.cc b/base/threading/thread_local_storage_unittest.cc
index 321a0584a969fe1afeedcd49435e2db7bf6d3da9..b53f57771580cf4cabca85e02c3f8e80cbc52314 100644
--- a/base/threading/thread_local_storage_unittest.cc
+++ b/base/threading/thread_local_storage_unittest.cc
@@ -33,9 +33,9 @@ class ThreadLocalStorageRunner : public DelegateSimpleThread::Delegate {
   explicit ThreadLocalStorageRunner(int* tls_value_ptr)
       : tls_value_ptr_(tls_value_ptr) {}
 
-  virtual ~ThreadLocalStorageRunner() {}
+  ~ThreadLocalStorageRunner() override {}
 
-  virtual void Run() override {
+  void Run() override {
     *tls_value_ptr_ = kInitialTlsValue;
     tls_slot.Set(tls_value_ptr_);