Standardize usage of virtual/override/final specifiers in base/.

base/sequence_checker_unittest.cc

Index: base/sequence_checker_unittest.cc
diff --git a/base/sequence_checker_unittest.cc b/base/sequence_checker_unittest.cc
index ad77db0999d2890215568530d329680c031ae850..9aae82c684aff1dabcb718e14d274ebcc6609b77 100644
--- a/base/sequence_checker_unittest.cc
+++ b/base/sequence_checker_unittest.cc
@@ -56,14 +56,12 @@ class SequenceCheckerTest : public testing::Test {
  public:
   SequenceCheckerTest() : other_thread_("sequence_checker_test_other_thread") {}
 
-  virtual ~SequenceCheckerTest() {}
-
-  virtual void SetUp() override {
+  void SetUp() override {
     other_thread_.Start();
     ResetPool();
   }
 
-  virtual void TearDown() override {
+  void TearDown() override {
     other_thread_.Stop();
     pool()->Shutdown();
   }