message: Set default max_threads_count to DVQA injection helper
  Cr-Commit-Position: refs/heads/master@{#32748}
diff: @@ -75,7 +75,7 @@ class VideoQualityAnalyzerInjectionHelper : public StatsObserverInterface {
  void Start(std::string test_case_name,
  rtc::ArrayView<const std::string> peer_names,
  - int max_threads_count);
  + int max_threads_count = 1);
  // Forwards |stats_reports| for Peer Connection |pc_label| to
  // |analyzer_|.
  