Googletest export

Fix -Wmismatched-tags error with struct tuple_size vs class tuple_size

PiperOrigin-RevId: 336930166

googletest/include/gtest/internal/gtest-internal.h

@@ -1325,8 +1325,8 @@ constexpr bool InstantiateTypedTestCase_P_IsDeprecated() { return true; }
 namespace std {
 
 template <typename... Ts>
-struct tuple_size<testing::internal::FlatTuple<Ts...>>
-    : std::integral_constant<size_t, sizeof...(Ts)> {};
+class tuple_size<testing::internal::FlatTuple<Ts...>>
+    : public std::integral_constant<size_t, sizeof...(Ts)> {};
 
 }  // namespace std