Check implementation files for virtual and OVERRIDE

tools/clang/plugins/tests/virtual_methods.cpp

-// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Copyright (c) 2012 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 "virtual_methods.h"
 
 // Shouldn't warn about method usage in the implementation file.
 class VirtualMethodsInImplementation {
  public:
   virtual void MethodIsAbstract() = 0;
   virtual void MethodHasNoArguments();
   virtual void MethodHasEmptyDefaultImpl() {}
   virtual bool ComplainAboutThis() { return true; }
 };
 
 // Stubs to fill in the abstract method
 class ConcreteVirtualMethodsInHeaders : public VirtualMethodsInHeaders {
  public:
-  virtual void MethodIsAbstract() {}
+  virtual void MethodIsAbstract() override {}
 };
 
 class ConcreteVirtualMethodsInImplementation
     : public VirtualMethodsInImplementation {
  public:
-  virtual void MethodIsAbstract() {}
+  virtual void MethodIsAbstract() override {}
 };
 
 // Fill in the implementations
 void VirtualMethodsInHeaders::MethodHasNoArguments() {}
 void WarnOnMissingVirtual::MethodHasNoArguments() {}
 void VirtualMethodsInImplementation::MethodHasNoArguments() {}
 
 int main() {
   ConcreteVirtualMethodsInHeaders one;
   ConcreteVirtualMethodsInImplementation two;
 }