Standardize usage of virtual/override/final in base/

base/files/file_path_watcher_browsertest.cc

Index: base/files/file_path_watcher_browsertest.cc
diff --git a/base/files/file_path_watcher_browsertest.cc b/base/files/file_path_watcher_browsertest.cc
index f6d6d333a0fb11f366010cdc4a2e2c7149d2c7fe..0e19b2ed9ae70d9aaf006c2b5f2608e7b85aea6b 100644
--- a/base/files/file_path_watcher_browsertest.cc
+++ b/base/files/file_path_watcher_browsertest.cc
@@ -111,9 +111,9 @@ class TestDelegate : public TestDelegateBase {
       : collector_(collector) {
     collector_->Register(this);
   }
-  virtual ~TestDelegate() {}
+  ~TestDelegate() override {}
 
-  virtual void OnFileChanged(const FilePath& path, bool error) override {
+  void OnFileChanged(const FilePath& path, bool error) override {
     if (error)
       ADD_FAILURE() << "Error " << path.value();
     else
@@ -272,9 +272,9 @@ class Deleter : public TestDelegateBase {
       : watcher_(watcher),
         loop_(loop) {
   }
-  virtual ~Deleter() {}
+  ~Deleter() override {}
 
-  virtual void OnFileChanged(const FilePath&, bool) override {
+  void OnFileChanged(const FilePath&, bool) override {
     watcher_.reset();
     loop_->PostTask(FROM_HERE, MessageLoop::QuitWhenIdleClosure());
   }