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

sync/engine/directory_commit_contribution_unittest.cc

Index: sync/engine/directory_commit_contribution_unittest.cc
diff --git a/sync/engine/directory_commit_contribution_unittest.cc b/sync/engine/directory_commit_contribution_unittest.cc
index be04c73c42068815b8188582a76cf38b8f6eaab7..b5612b6d66c9c1fb88db5023460d507fa71a17e7 100644
--- a/sync/engine/directory_commit_contribution_unittest.cc
+++ b/sync/engine/directory_commit_contribution_unittest.cc
@@ -20,7 +20,7 @@ namespace syncer {
 
 class DirectoryCommitContributionTest : public ::testing::Test {
  public:
-  virtual void SetUp() override {
+  void SetUp() override {
     dir_maker_.SetUp();
 
     syncable::WriteTransaction trans(FROM_HERE, syncable::UNITTEST, dir());
@@ -30,9 +30,7 @@ class DirectoryCommitContributionTest : public ::testing::Test {
     CreateTypeRoot(&trans, dir(), BOOKMARKS);
   }
 
-  virtual void TearDown() override {
-    dir_maker_.TearDown();
-  }
+  void TearDown() override { dir_maker_.TearDown(); }
 
  protected:
   int64 CreateUnsyncedItemWithAttachments(