replace OVERRIDE and FINAL with override and final in base/

base/files/important_file_writer_unittest.cc

Index: base/files/important_file_writer_unittest.cc
diff --git a/base/files/important_file_writer_unittest.cc b/base/files/important_file_writer_unittest.cc
index c55f0cc037f2e8ade017cbdd4d089b3a03517135..71242eeaabe59d5ded63d6696bde84371f848364 100644
--- a/base/files/important_file_writer_unittest.cc
+++ b/base/files/important_file_writer_unittest.cc
@@ -33,7 +33,7 @@ class DataSerializer : public ImportantFileWriter::DataSerializer {
   explicit DataSerializer(const std::string& data) : data_(data) {
   }
 
-  virtual bool SerializeData(std::string* output) OVERRIDE {
+  virtual bool SerializeData(std::string* output) override {
     output->assign(data_);
     return true;
   }