Update plugin to handle new style rules for virtual annotations.

tools/clang/plugins/tests/virtual_methods.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 VIRTUAL_METHODS_H_
-#define VIRTUAL_METHODS_H_
-
-// Should warn about virtual method usage.
-class VirtualMethodsInHeaders {
- public:
-  // Don't complain about these.
-  virtual void MethodIsAbstract() = 0;
-  virtual void MethodHasNoArguments();
-  virtual void MethodHasEmptyDefaultImpl() {}
-
-  // But complain about this:
-  virtual bool ComplainAboutThis() { return true; }
-};
-
-// Complain on missing 'virtual' keyword in overrides.
-class WarnOnMissingVirtual : public VirtualMethodsInHeaders {
- public:
-  void MethodHasNoArguments() override;
-};
-
-// Don't complain about things in a 'testing' namespace.
-namespace testing {
-struct TestStruct {};
-}  // namespace testing
-
-class VirtualMethodsInHeadersTesting : public VirtualMethodsInHeaders {
- public:
-  // Don't complain about no virtual testing methods.
-  void MethodHasNoArguments();
- private:
-  testing::TestStruct tester_;
-};
-
-#endif  // VIRTUAL_METHODS_H_