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

base/prefs/pref_notifier_impl_unittest.cc

Index: base/prefs/pref_notifier_impl_unittest.cc
diff --git a/base/prefs/pref_notifier_impl_unittest.cc b/base/prefs/pref_notifier_impl_unittest.cc
index 04564c83d2bb94cee234eb2cfd309edb51458695..0ecf138d17599d9a4d5d00087ff2c4ea2307d926 100644
--- a/base/prefs/pref_notifier_impl_unittest.cc
+++ b/base/prefs/pref_notifier_impl_unittest.cc
@@ -85,7 +85,7 @@ class PrefObserverMock : public PrefObserver {
 // Test fixture class.
 class PrefNotifierTest : public testing::Test {
  protected:
-  virtual void SetUp() {
+  void SetUp() override {
     pref_service_.registry()->RegisterBooleanPref(kChangedPref, true);
     pref_service_.registry()->RegisterBooleanPref(kUnchangedPref, true);
   }