Standardize usage of virtual/override/final in base/

base/threading/thread_checker_unittest.cc

Index: base/threading/thread_checker_unittest.cc
diff --git a/base/threading/thread_checker_unittest.cc b/base/threading/thread_checker_unittest.cc
index 1084dd92d177b32d9c79ada39e877acabd15728b..d42cbc26278acc02a5b3eaffdb171a2cc5a25172 100644
--- a/base/threading/thread_checker_unittest.cc
+++ b/base/threading/thread_checker_unittest.cc
@@ -52,9 +52,7 @@ class CallDoStuffOnThread : public base::SimpleThread {
         thread_checker_class_(thread_checker_class) {
   }
 
-  virtual void Run() override {
-    thread_checker_class_->DoStuff();
-  }
+  void Run() override { thread_checker_class_->DoStuff(); }
 
  private:
   ThreadCheckerClass* thread_checker_class_;
@@ -71,9 +69,7 @@ class DeleteThreadCheckerClassOnThread : public base::SimpleThread {
         thread_checker_class_(thread_checker_class) {
   }
 
-  virtual void Run() override {
-    thread_checker_class_.reset();
-  }
+  void Run() override { thread_checker_class_.reset(); }
 
  private:
   scoped_ptr<ThreadCheckerClass> thread_checker_class_;