Wire up BWE stats through WebrtcSession so that they are filled in both for audio and video calls.

webrtc/pc/rtcstatscollector.h

Index: webrtc/pc/rtcstatscollector.h
diff --git a/webrtc/pc/rtcstatscollector.h b/webrtc/pc/rtcstatscollector.h
index 48e66baf7eaf2222d5d59cc478cc46f0be34bfad..9e45356c54d6494f206a946a29e06fa4f103a952 100644
--- a/webrtc/pc/rtcstatscollector.h
+++ b/webrtc/pc/rtcstatscollector.h
@@ -26,6 +26,7 @@
 #include "webrtc/base/sigslot.h"
 #include "webrtc/base/sslidentity.h"
 #include "webrtc/base/timeutils.h"
+#include "webrtc/call/call.h"
 #include "webrtc/media/base/mediachannel.h"
 #include "webrtc/pc/datachannel.h"
 #include "webrtc/pc/trackmediainfomap.h"
@@ -75,7 +76,9 @@ class RTCStatsCollector : public virtual rtc::RefCountInterface,
   // Stats gathering on a particular thread. Calls |AddPartialResults| before
   // returning. Virtual for the sake of testing.
   virtual void ProducePartialResultsOnSignalingThread(int64_t timestamp_us);
-  virtual void ProducePartialResultsOnNetworkThread(int64_t timestamp_us);
+  virtual void ProducePartialResultsOnNetworkThread(
+      int64_t timestamp_us,
+      const Call::Stats& call_stats);
 
   // Can be called on any thread.
   void AddPartialResults(
@@ -104,8 +107,10 @@ class RTCStatsCollector : public virtual rtc::RefCountInterface,
       int64_t timestamp_us, RTCStatsReport* report) const;
   // Produces |RTCIceCandidatePairStats| and |RTCIceCandidateStats|.
   void ProduceIceCandidateAndPairStats_n(
-      int64_t timestamp_us, const SessionStats& session_stats,
+      int64_t timestamp_us,
+      const SessionStats& session_stats,
       const cricket::VideoMediaInfo* video_media_info,
+      const Call::Stats& call_stats,
       RTCStatsReport* report) const;
   // Produces |RTCMediaStreamStats| and |RTCMediaStreamTrackStats|.
   void ProduceMediaStreamAndTrackStats_s(