Standardize usage of virtual/override/final in chrome/

chrome/test/base/view_event_test_platform_part_mac.mm

 // 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 "chrome/test/base/view_event_test_platform_part.h"
 
 namespace {
 
 // ViewEventTestPlatformPart implementation for toolkit-views on Mac.
 class ViewEventTestPlatformPartMac : public ViewEventTestPlatformPart {
  public:
   ViewEventTestPlatformPartMac() {}
 
   // Overridden from ViewEventTestPlatformPart:
-  virtual gfx::NativeWindow GetContext() override { return NULL; }
+  gfx::NativeWindow GetContext() override { return NULL; }
 
  private:
   DISALLOW_COPY_AND_ASSIGN(ViewEventTestPlatformPartMac);
 };
 
 }  // namespace
 
 // static
 ViewEventTestPlatformPart* ViewEventTestPlatformPart::Create(
     ui::ContextFactory* context_factory) {
   return new ViewEventTestPlatformPartMac();
 }