RTCStatsCollector: Utilize network thread to minimize thread hops.

webrtc/api/webrtcsession.h

Index: webrtc/api/webrtcsession.h
diff --git a/webrtc/api/webrtcsession.h b/webrtc/api/webrtcsession.h
index 1aa3e187ae2bf5f2e320ca6c43d5fee44708446f..b433ab672b2b81d294d81718b22ec84ec203e73f 100644
--- a/webrtc/api/webrtcsession.h
+++ b/webrtc/api/webrtcsession.h
@@ -115,6 +115,20 @@ struct SessionStats {
   TransportStatsMap transport_stats;
 };
 
+struct ChannelNamePair {
+  ChannelNamePair(
+      const std::string& content_name, const std::string& transport_name)
+      : content_name(content_name), transport_name(transport_name) {}
+  std::string content_name;
+  std::string transport_name;
+};
+
+struct ChannelNamePairs {
+  rtc::Optional<ChannelNamePair> voice;
+  rtc::Optional<ChannelNamePair> video;
+  rtc::Optional<ChannelNamePair> data;
+};
+
 // A WebRtcSession manages general session state. This includes negotiation
 // of both the application-level and network-level protocols:  the former
 // defines what will be sent and the latter defines how it will be sent.  Each
@@ -194,6 +208,7 @@ class WebRtcSession :
   virtual cricket::DataChannel* data_channel() {
     return data_channel_.get();
   }
+  std::unique_ptr<ChannelNamePairs> GetChannelNamePairs();
 
   cricket::BaseChannel* GetChannel(const std::string& content_name);
 
@@ -263,6 +278,8 @@ class WebRtcSession :
   // Returns stats for all channels of all transports.
   // This avoids exposing the internal structures used to track them.
   virtual bool GetTransportStats(SessionStats* stats);
+  virtual std::unique_ptr<SessionStats> GetSessionStats_n(
+      const ChannelNamePairs& channel_name_pairs);
 
   // Get stats for a specific channel
   bool GetChannelTransportStats(cricket::BaseChannel* ch, SessionStats* stats);
@@ -271,10 +288,15 @@ class WebRtcSession :
   virtual bool GetLocalCertificate(
       const std::string& transport_name,
       rtc::scoped_refptr<rtc::RTCCertificate>* certificate);
+  virtual bool GetLocalCertificate_n(
+      const std::string& transport_name,
+      rtc::scoped_refptr<rtc::RTCCertificate>* certificate);
 
   // Caller owns returned certificate
   virtual std::unique_ptr<rtc::SSLCertificate> GetRemoteSSLCertificate(
       const std::string& transport_name);
+  virtual std::unique_ptr<rtc::SSLCertificate> GetRemoteSSLCertificate_n(
+      const std::string& transport_name);
 
   cricket::DataChannelType data_channel_type() const;
 
@@ -486,7 +508,7 @@ class WebRtcSession :
   const std::string sid_;
   bool initial_offerer_ = false;
 
-  std::unique_ptr<cricket::TransportController> transport_controller_;
+  const std::unique_ptr<cricket::TransportController> transport_controller_;
   MediaControllerInterface* media_controller_;
   std::unique_ptr<cricket::VoiceChannel> voice_channel_;
   std::unique_ptr<cricket::VideoChannel> video_channel_;