Standardize usage of virtual/override/final specifiers.

ui/events/platform/x11/x11_event_source_glib.cc

 // Copyright 2014 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.
 
 #include "ui/events/platform/x11/x11_event_source.h"
 
 #include <glib.h>
 #include <X11/Xlib.h>
 
 namespace ui {
@@ skipping 37 matching lines @@
 };
 
 class X11EventSourceGlib : public X11EventSource {
  public:
   explicit X11EventSourceGlib(XDisplay* display)
       : X11EventSource(display),
         x_source_(NULL) {
     InitXSource(ConnectionNumber(display));
   }
 
-  virtual ~X11EventSourceGlib() {
+  ~X11EventSourceGlib() override {
     g_source_destroy(x_source_);
     g_source_unref(x_source_);
   }
 
  private:
   void InitXSource(int fd) {
     CHECK(!x_source_);
     CHECK(display()) << "Unable to get connection to X server";
 
     x_poll_.reset(new GPollFD());
@@ skipping 23 matching lines @@
 };
 
 }  // namespace
 
 scoped_ptr<PlatformEventSource> PlatformEventSource::CreateDefault() {
   return scoped_ptr<PlatformEventSource>(
       new X11EventSourceGlib(gfx::GetXDisplay()));
 }
 
 }  // namespace ui