Add tracing to interesting media-related methods.

webrtc/pc/channel.cc

Index: webrtc/pc/channel.cc
diff --git a/webrtc/pc/channel.cc b/webrtc/pc/channel.cc
index 1d5d159d05fd786eafc6fb909fb96298d64e3c52..3bdb5cfb82f2b2e1947aafad16c6a8d976586147 100644
--- a/webrtc/pc/channel.cc
+++ b/webrtc/pc/channel.cc
@@ -177,6 +177,7 @@ BaseChannel::BaseChannel(rtc::Thread* thread,
 }
 
 BaseChannel::~BaseChannel() {
+  TRACE_EVENT0("webrtc", "BaseChannel::~BaseChannel");
   ASSERT(worker_thread_ == rtc::Thread::Current());
   Deinit();
   StopConnectionMonitor();
@@ -1014,6 +1015,7 @@ bool BaseChannel::SetSrtp_w(const std::vector<CryptoParams>& cryptos,
                             ContentAction action,
                             ContentSource src,
                             std::string* error_desc) {
+  TRACE_EVENT0("webrtc", "BaseChannel::SetSrtp_w");
   if (action == CA_UPDATE) {
     // no crypto params.
     return true;
@@ -1325,6 +1327,7 @@ VoiceChannel::VoiceChannel(rtc::Thread* thread,
       received_media_(false) {}
 
 VoiceChannel::~VoiceChannel() {
+  TRACE_EVENT0("webrtc", "VoiceChannel::~VoiceChannel");
   StopAudioMonitor();
   StopMediaMonitor();
   // this can't be done in the base class, since it calls a virtual
@@ -1643,6 +1646,7 @@ bool VideoChannel::Init() {
 }
 
 VideoChannel::~VideoChannel() {
+  TRACE_EVENT0("webrtc", "VideoChannel::~VideoChannel");
   std::vector<uint32_t> screencast_ssrcs;
   ScreencastMap::iterator iter;
   while (!screencast_capturers_.empty()) {
@@ -1949,6 +1953,7 @@ DataChannel::DataChannel(rtc::Thread* thread,
       ready_to_send_data_(false) {}
 
 DataChannel::~DataChannel() {
+  TRACE_EVENT0("webrtc", "DataChannel::~DataChannel");
   StopMediaMonitor();
   // this can't be done in the base class, since it calls a virtual
   DisableMedia_w();