Add virtual and OVERRIDE to base/ implementation files

base/synchronization/waitable_event_watcher_unittest.cc

Index: base/synchronization/waitable_event_watcher_unittest.cc
diff --git a/base/synchronization/waitable_event_watcher_unittest.cc b/base/synchronization/waitable_event_watcher_unittest.cc
index ee9478ab9ed571a47a1f9e2dd5732f817c9245b6..ea755c1aa82b6b83edafc96f50501547402b8e07 100644
--- a/base/synchronization/waitable_event_watcher_unittest.cc
+++ b/base/synchronization/waitable_event_watcher_unittest.cc
@@ -14,7 +14,7 @@ namespace {
 
 class QuitDelegate : public WaitableEventWatcher::Delegate {
  public:
-  virtual void OnWaitableEventSignaled(WaitableEvent* event) {
+  virtual void OnWaitableEventSignaled(WaitableEvent* event) OVERRIDE {
     MessageLoop::current()->Quit();
   }
 };
@@ -23,7 +23,7 @@ class DecrementCountDelegate : public WaitableEventWatcher::Delegate {
  public:
   explicit DecrementCountDelegate(int* counter) : counter_(counter) {
   }
-  virtual void OnWaitableEventSignaled(WaitableEvent* object) {
+  virtual void OnWaitableEventSignaled(WaitableEvent* object) OVERRIDE {
     --(*counter_);
   }
  private: