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

base/message_loop/message_loop_proxy_impl_unittest.cc

Index: base/message_loop/message_loop_proxy_impl_unittest.cc
diff --git a/base/message_loop/message_loop_proxy_impl_unittest.cc b/base/message_loop/message_loop_proxy_impl_unittest.cc
index 5f31140303f91d439aa5cd61bb9793de4ac31d7b..fa253717654e7f081d5d452f94bd731fedb594da 100644
--- a/base/message_loop/message_loop_proxy_impl_unittest.cc
+++ b/base/message_loop/message_loop_proxy_impl_unittest.cc
@@ -38,14 +38,14 @@ class MessageLoopProxyImplTest : public testing::Test {
   }
 
  protected:
-  virtual void SetUp() override {
+  void SetUp() override {
     io_thread_.reset(new Thread("MessageLoopProxyImplTest_IO"));
     file_thread_.reset(new Thread("MessageLoopProxyImplTest_File"));
     io_thread_->Start();
     file_thread_->Start();
   }
 
-  virtual void TearDown() override {
+  void TearDown() override {
     io_thread_->Stop();
     file_thread_->Stop();
   }