Use std::string references instead of copying contents.

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 2533328968945e4c2c67a2694e95ae8d19c288ea..19455621553590362db12916a40ee82b8614cef7 100644
--- a/talk/app/webrtc/webrtcsession.cc
+++ b/talk/app/webrtc/webrtcsession.cc
@@ -1581,7 +1581,7 @@ void WebRtcSession::RemoveUnusedChannelsAndTransports(
   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);
   }
@@ -1591,7 +1591,7 @@ void WebRtcSession::RemoveUnusedChannelsAndTransports(
   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);
@@ -1602,7 +1602,7 @@ void WebRtcSession::RemoveUnusedChannelsAndTransports(
   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);
   }