Improved check for trivial templates.

tools/clang/plugins/tests/trivial_ctor.cpp

+// Copyright (c) 2016 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 "trivial_ctor.h"
+
+// Due to https://bugs.chromium.org/p/chromium/issues/detail?id=663463, we treat
+// templated classes/structs as non-trivial, even if they really are trivial.
+// Thus, classes that have such a class/struct as a member get flagged as being
+// themselves non-trivial, even if (like |MySpinLock|) they are. Special-case
+// [std::]atomic_int.
+class TrivialTemplateOK {
+ public:
+ private:
+  MySpinLock lock_;
+};
+
+int main() {
+  TrivialTemplateOK one;
+  return 0;
+}