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

sync/engine/syncer_unittest.cc

Index: sync/engine/syncer_unittest.cc
diff --git a/sync/engine/syncer_unittest.cc b/sync/engine/syncer_unittest.cc
index f8682a67cd2d74cc4d229fb981c9aca570a661c9..965728b312cf2ba9006e94c352dbf69246e51545 100644
--- a/sync/engine/syncer_unittest.cc
+++ b/sync/engine/syncer_unittest.cc
@@ -277,7 +277,7 @@ class SyncerTest : public testing::Test,
             session_.get()));
   }
 
-  virtual void SetUp() {
+  void SetUp() override {
     dir_maker_.SetUp();
     mock_server_.reset(new MockConnectionManager(directory(),
                                                  &cancelation_signal_));
@@ -324,7 +324,7 @@ class SyncerTest : public testing::Test,
     mock_server_->SetKeystoreKey("encryption_key");
   }
 
-  virtual void TearDown() {
+  void TearDown() override {
     model_type_registry_->UnregisterDirectoryTypeDebugInfoObserver(
         &debug_info_cache_);
     mock_server_.reset();