Use std::string references instead of copying contents.

talk/app/webrtc/webrtcsession.cc

 /*
  * libjingle
  * Copyright 2012 Google Inc.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
  *
  *  1. Redistributions of source code must retain the above copyright notice,
  *     this list of conditions and the following disclaimer.
  *  2. Redistributions in binary form must reproduce the above copyright notice,
@@ skipping 1563 matching lines @@
 
 void WebRtcSession::RemoveUnusedChannelsAndTransports(
     const SessionDescription* desc) {
   // Destroy video_channel_ first since it may have a pointer to the
   // voice_channel_.
   const cricket::ContentInfo* video_info =
       cricket::GetFirstVideoContent(desc);
   if ((!video_info || video_info->rejected) && video_channel_) {
     mediastream_signaling_->OnVideoChannelClose();
     SignalVideoChannelDestroyed();
-    const std::string content_name = video_channel_->content_name();
+    const std::string& content_name = video_channel_->content_name();

[joachim, 2015/07/16 08:21:47]

This caused the failures on the try-bots. After the channel was released, the
string reference pointed to released memory.

     channel_manager_->DestroyVideoChannel(video_channel_.release());
     DestroyTransportProxy(content_name);
   }
 
   const cricket::ContentInfo* voice_info =
       cricket::GetFirstAudioContent(desc);
   if ((!voice_info || voice_info->rejected) && voice_channel_) {
     mediastream_signaling_->OnAudioChannelClose();
     SignalVoiceChannelDestroyed();
-    const std::string content_name = voice_channel_->content_name();
+    const std::string& content_name = voice_channel_->content_name();
     channel_manager_->DestroyVoiceChannel(voice_channel_.release(),
                                           video_channel_.get());
     DestroyTransportProxy(content_name);
   }
 
   const cricket::ContentInfo* data_info =
       cricket::GetFirstDataContent(desc);
   if ((!data_info || data_info->rejected) && data_channel_) {
     mediastream_signaling_->OnDataChannelClose();
     SignalDataChannelDestroyed();
-    const std::string content_name = data_channel_->content_name();
+    const std::string& content_name = data_channel_->content_name();
     channel_manager_->DestroyDataChannel(data_channel_.release());
     DestroyTransportProxy(content_name);
   }
 }
 
 // TODO(mallinath) - Add a correct error code if the channels are not creatued
 // due to BUNDLE is enabled but rtcp-mux is disabled.
 bool WebRtcSession::CreateChannels(const SessionDescription* desc) {
   // Creating the media channels and transport proxies.
   const cricket::ContentInfo* voice = cricket::GetFirstAudioContent(desc);
@@ skipping 344 matching lines @@
 
   if (!srtp_cipher.empty()) {
     metrics_observer_->AddHistogramSample(srtp_name, srtp_cipher);
   }
   if (!ssl_cipher.empty()) {
     metrics_observer_->AddHistogramSample(ssl_name, ssl_cipher);
   }
 }
 
 }  // namespace webrtc