message: WindowCapturerWinGdi shouldn't deliver SUCCESS and nullptr.
  Consumers expect the frame to be valid if Result::SUCCESS is delivered.
  If the frame is nullptr, we should deliver ERROR_TEMPORARY instead.
  Cr-Commit-Position: refs/heads/main@{#37590}
diff: @@ -160,17 +160,17 @@ void WindowCapturerWinGdi::CaptureFrame() {
  int64_t capture_start_time_nanos = rtc::TimeNanos();
  CaptureResults results = CaptureFrame(/*capture_owned_windows*/ true);
  + if (!results.frame) {
  + callback_->OnCaptureResult(Result::ERROR_TEMPORARY, nullptr);
  + return;
  + }
  - if (results.frame) {
  int capture_time_ms = (rtc::TimeNanos() - capture_start_time_nanos) /
  rtc::kNumNanosecsPerMillisec;
  RTC_HISTOGRAM_COUNTS_1000(
  - "WebRTC.DesktopCapture.Win.WindowGdiCapturerFrameTime",
  - capture_time_ms);
  + "WebRTC.DesktopCapture.Win.WindowGdiCapturerFrameTime", capture_time_ms);
  results.frame->set_capture_time_ms(capture_time_ms);
  results.frame->set_capturer_id(DesktopCapturerId::kWindowCapturerWinGdi);
  - }
  -
  callback_->OnCaptureResult(results.result, std::move(results.frame));
  }
  