win: Fix a few clang style plugin warnings.

base/win/object_watcher.h

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef BASE_WIN_OBJECT_WATCHER_H_
 #define BASE_WIN_OBJECT_WATCHER_H_
 
 #include <windows.h>
 
 #include "base/base_export.h"
@@ skipping 38 matching lines @@
  public:
   class BASE_EXPORT Delegate {
    public:
     virtual ~Delegate() {}
     // Called from the MessageLoop when a signaled object is detected.  To
     // continue watching the object, StartWatching must be called again.
     virtual void OnObjectSignaled(HANDLE object) = 0;
   };
 
   ObjectWatcher();
-  ~ObjectWatcher();
+  ~ObjectWatcher() override;
 
   // When the object is signaled, the given delegate is notified on the thread
   // where StartWatching is called.  The ObjectWatcher is not responsible for
   // deleting the delegate.
   //
   // Returns true if the watch was started.  Otherwise, false is returned.
   //
   bool StartWatching(HANDLE object, Delegate* delegate);
 
   // Stops watching.  Does nothing if the watch has already completed.  If the
@@ skipping 10 matching lines @@
   // Returns the handle of the object being watched.
   HANDLE GetWatchedObject() const;
 
  private:
   // Called on a background thread when done waiting.
   static void CALLBACK DoneWaiting(void* param, BOOLEAN timed_out);
 
   void Signal(Delegate* delegate);
 
   // MessageLoop::DestructionObserver implementation:
-  virtual void WillDestroyCurrentMessageLoop();
+  void WillDestroyCurrentMessageLoop() override;
 
   // Internal state.
   Closure callback_;
   HANDLE object_;             // The object being watched
   HANDLE wait_object_;        // Returned by RegisterWaitForSingleObject
   MessageLoop* origin_loop_;  // Used to get back to the origin thread
 
   WeakPtrFactory<ObjectWatcher> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ObjectWatcher);
 };
 
 }  // namespace win
 }  // namespace base
 
 #endif  // BASE_WIN_OBJECT_WATCHER_H_