Cleanup: Pass std::string as const reference from content/

content/renderer/media/rtc_peer_connection_handler.cc

Index: content/renderer/media/rtc_peer_connection_handler.cc
diff --git a/content/renderer/media/rtc_peer_connection_handler.cc b/content/renderer/media/rtc_peer_connection_handler.cc
index 181838af564e9d0086921219e6c6eebed4a4e011..33ff2a29157c3db11687a98c3a73c088560bc8f9 100644
--- a/content/renderer/media/rtc_peer_connection_handler.cc
+++ b/content/renderer/media/rtc_peer_connection_handler.cc
@@ -495,7 +495,8 @@ void GetStatsOnSignalingThread(
     const scoped_refptr<webrtc::PeerConnectionInterface>& pc,
     webrtc::PeerConnectionInterface::StatsOutputLevel level,
     const scoped_refptr<webrtc::StatsObserver>& observer,
-    const std::string track_id, blink::WebMediaStreamSource::Type track_type) {
+    const std::string& track_id,
+    blink::WebMediaStreamSource::Type track_type) {
   TRACE_EVENT0("webrtc", "GetStatsOnSignalingThread");
 
   scoped_refptr<webrtc::MediaStreamTrackInterface> track;