Building error in Android P after commit ef3c797d

Here is the building error introduced by ef3c797d "drm_hwcomposer: Add backend-dependent validation for HwcDisplay class"

Android.bp has cppflag -DHWC2_USE_CPP11

Please fix build with Android P

external/drm_hwcomposer/backend/Backend.cpp:115:15: error: decomposition declarations are a C++17 extension [-Werror,-Wc++17-extensions]
  for (auto & [ z_order, layer ] : z_map) {
              ^~~~~~~~~~~~~~~~~~
1 error generated.