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

base/tracked_objects_unittest.cc

Index: base/tracked_objects_unittest.cc
diff --git a/base/tracked_objects_unittest.cc b/base/tracked_objects_unittest.cc
index f19ba7b2c63a1960a95868ccc3695e7cd99411ff..b6fc851824e4efe66ae67f845501774b7637d92c 100644
--- a/base/tracked_objects_unittest.cc
+++ b/base/tracked_objects_unittest.cc
@@ -34,7 +34,7 @@ class TrackedObjectsTest : public testing::Test {
     ThreadData::now_function_is_time_ = true;
   }
 
-  virtual ~TrackedObjectsTest() {
+  ~TrackedObjectsTest() override {
     // We should not need to leak any structures we create, since we are
     // single threaded, and carefully accounting for items.
     ThreadData::ShutdownSingleThreadedCleanup(false);