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

base/json/json_value_serializer_unittest.cc

Index: base/json/json_value_serializer_unittest.cc
diff --git a/base/json/json_value_serializer_unittest.cc b/base/json/json_value_serializer_unittest.cc
index dc436937a3316cbcfa3b2219c6bc50a058ab602b..e3c349c2c03bb4be305a3b11f0c53a8a3855a4e9 100644
--- a/base/json/json_value_serializer_unittest.cc
+++ b/base/json/json_value_serializer_unittest.cc
@@ -372,9 +372,7 @@ TEST(JSONValueSerializerTest, JSONReaderComments) {
 
 class JSONFileValueSerializerTest : public testing::Test {
  protected:
-  virtual void SetUp() override {
-    ASSERT_TRUE(temp_dir_.CreateUniqueTempDir());
-  }
+  void SetUp() override { ASSERT_TRUE(temp_dir_.CreateUniqueTempDir()); }
 
   base::ScopedTempDir temp_dir_;
 };