Standardize usage of virtual/override/final in base/

base/synchronization/waitable_event_watcher_posix.cc

Index: base/synchronization/waitable_event_watcher_posix.cc
diff --git a/base/synchronization/waitable_event_watcher_posix.cc b/base/synchronization/waitable_event_watcher_posix.cc
index e791871693fc7c8c1231f6857020c27a1330f418..6fc337cc81b420b504cef3be0d7194557082d86d 100644
--- a/base/synchronization/waitable_event_watcher_posix.cc
+++ b/base/synchronization/waitable_event_watcher_posix.cc
@@ -65,7 +65,7 @@ class AsyncWaiter : public WaitableEvent::Waiter {
         callback_(callback),
         flag_(flag) { }
 
-  virtual bool Fire(WaitableEvent* event) override {
+  bool Fire(WaitableEvent* event) override {
     // Post the callback if we haven't been cancelled.
     if (!flag_->value()) {
       message_loop_->PostTask(FROM_HERE, callback_);
@@ -81,9 +81,7 @@ class AsyncWaiter : public WaitableEvent::Waiter {
   }
 
   // See StopWatching for discussion
-  virtual bool Compare(void* tag) override {
-    return tag == flag_.get();
-  }
+  bool Compare(void* tag) override { return tag == flag_.get(); }
 
  private:
   MessageLoop *const message_loop_;