Add tracing to upper-level WebRTC calls.

talk/app/webrtc/webrtcsession.cc

Index: talk/app/webrtc/webrtcsession.cc
diff --git a/talk/app/webrtc/webrtcsession.cc b/talk/app/webrtc/webrtcsession.cc
index ec0456f7cb9f1f8743dabc4794f181353369f439..d3e8dc5596555eed648ca8bc8dc699cda3a9517b 100644
--- a/talk/app/webrtc/webrtcsession.cc
+++ b/talk/app/webrtc/webrtcsession.cc
@@ -50,6 +50,7 @@
 #include "webrtc/base/logging.h"
 #include "webrtc/base/stringencode.h"
 #include "webrtc/base/stringutils.h"
+#include "webrtc/base/trace_event.h"
 #include "webrtc/call.h"
 #include "webrtc/p2p/base/portallocator.h"
 #include "webrtc/p2p/base/transportchannel.h"
@@ -790,6 +791,7 @@ void WebRtcSession::CreateAnswer(
 
 bool WebRtcSession::SetLocalDescription(SessionDescriptionInterface* desc,
                                         std::string* err_desc) {
+  TRACE_EVENT0("webrtc", "WebRtcSession::SetLocalDescription");
   ASSERT(signaling_thread()->IsCurrent());
 
   // Takes the ownership of |desc| regardless of the result.
@@ -844,6 +846,7 @@ bool WebRtcSession::SetLocalDescription(SessionDescriptionInterface* desc,
 
 bool WebRtcSession::SetRemoteDescription(SessionDescriptionInterface* desc,
                                          std::string* err_desc) {
+  TRACE_EVENT0("webrtc", "WebRtcSession::SetRemoteDescription");
   ASSERT(signaling_thread()->IsCurrent());
 
   // Takes the ownership of |desc| regardless of the result.