RTCRTPStreamStats.ssrc changed type to uint32_t.

As per PR: https://github.com/w3c/webrtc-stats/pull/157

BUG=webrtc:7065, webrtc:7066

Review-Url: https://codereview.webrtc.org/2675583003
Cr-Commit-Position: refs/heads/master@{#16471}
diff --git a/webrtc/pc/rtcstatscollector.cc b/webrtc/pc/rtcstatscollector.cc
index 38b729a..d1602d6 100644
--- a/webrtc/pc/rtcstatscollector.cc
+++ b/webrtc/pc/rtcstatscollector.cc
@@ -196,7 +196,7 @@
     const cricket::MediaReceiverInfo& media_receiver_info,
     RTCInboundRTPStreamStats* inbound_stats) {
   RTC_DCHECK(inbound_stats);
-  inbound_stats->ssrc = rtc::ToString<>(media_receiver_info.ssrc());
+  inbound_stats->ssrc = media_receiver_info.ssrc();
   // TODO(hbos): Support the remote case. crbug.com/657855
   inbound_stats->is_remote = false;
   inbound_stats->packets_received =
@@ -252,7 +252,7 @@
     const cricket::MediaSenderInfo& media_sender_info,
     RTCOutboundRTPStreamStats* outbound_stats) {
   RTC_DCHECK(outbound_stats);
-  outbound_stats->ssrc = rtc::ToString<>(media_sender_info.ssrc());
+  outbound_stats->ssrc = media_sender_info.ssrc();
   // TODO(hbos): Support the remote case. crbug.com/657856
   outbound_stats->is_remote = false;
   outbound_stats->packets_sent =