Treat std::atomic_int as a trivial class member when checking for non-trivial classes.

tools/clang/plugins/tests/virtual_bodies.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_
+#ifndef VIRTUAL_BODIES_H_
+#define VIRTUAL_BODIES_H_
 
 // Note: This is not actual windows.h but the stub file in system/windows.h
 #include <windows.h>
 
 #define CR_BEGIN_MSG_MAP_EX(theClass) virtual int f() { return 4; }
 #define BEGIN_SAFE_MSG_MAP_EX(theClass) virtual int g() { return 4; }
 
 // Should warn about virtual method usage.
 class VirtualMethodsInHeaders {
  public:
@@ skipping 23 matching lines @@
 
 class VirtualMethodsInHeadersTesting : public VirtualMethodsInHeaders {
  public:
   // Don't complain about no virtual testing methods.
   void MethodHasNoArguments();
 
  private:
   testing::TestStruct tester_;
 };
 
-#endif  // VIRTUAL_METHODS_H_
+#endif  // VIRTUAL_BODIES_H_