Can kDelta views be registered for export

[zhongchun]

In the view_descriptor.cc, we can see like this:

void ViewDescriptor::RegisterForExport() const {
  if (aggregation_window_.type() == AggregationWindow::Type::kCumulative) {
    StatsExporterImpl::Get()->AddView(*this);
  } else {
    std::cerr << "Only cumulative views may be registered for export.\n";
  }
}

Only cumulative views may be registered for export.
I modify this and find kDelta views can be registered for export and work well.
So i am a little confused, why opencensus don't support kDelta views to report.

[bubcool86]

In the view_descriptor.cc, we can see like this:

void ViewDescriptor::RegisterForExport() const {
  if (aggregation_window_.type() == AggregationWindow::Type::kCumulative) {
    StatsExporterImpl::Get()->AddView(*this);
  } else {
    std::cerr << "Only cumulative views may be registered for export.\n";
  }
}

Only cumulative views may be registered for export.
I modify this and find kDelta views can be registered for export and work well.
So i am a little confused, why opencensus don't support kDelta views to report.#456 (comment)