message: Use std::nullptr_t in place of nullptr_t.
  (It's not clear to me why only some projects/compilers are complaining
  but other parts of the code are using the explicit namespace.)
diff: @@ -97,8 +97,8 @@ namespace dawn {
  return static_cast<Derived&>(*this);
  }
  - ObjectBase(nullptr_t) {}
  - Derived& operator=(nullptr_t) {
  + ObjectBase(std::nullptr_t) {}
  + Derived& operator=(std::nullptr_t) {
  if (mHandle != nullptr) {
  Derived::DawnRelease(mHandle);
  mHandle = nullptr;
  