Reland of Free SCTP data channels asynchronously in PeerConnection.

talk/app/webrtc/peerconnection.cc

Index: talk/app/webrtc/peerconnection.cc
diff --git a/talk/app/webrtc/peerconnection.cc b/talk/app/webrtc/peerconnection.cc
index 933dc83c25642278d49a9491c2818a57f74fd217..2a5d52f80d0483ed8258c387c29358aedba0bf7d 100644
--- a/talk/app/webrtc/peerconnection.cc
+++ b/talk/app/webrtc/peerconnection.cc
@@ -107,6 +107,7 @@ enum {
   MSG_SET_SESSIONDESCRIPTION_FAILED,
   MSG_CREATE_SESSIONDESCRIPTION_FAILED,
   MSG_GETSTATS,
+  MSG_FREE_DATACHANNELS,
 };
 
 struct SetSessionDescriptionMsg : public rtc::MessageData {
@@ -1329,6 +1330,10 @@ void PeerConnection::OnMessage(rtc::Message* msg) {
       delete param;
       break;
     }
+    case MSG_FREE_DATACHANNELS: {
+      sctp_data_channels_to_free_.clear();
+      break;
+    }
     default:
       RTC_DCHECK(false && "Not implemented");
       break;
@@ -1908,7 +1913,11 @@ void PeerConnection::OnSctpDataChannelClosed(DataChannel* channel) {
       if (channel->id() >= 0) {
         sid_allocator_.ReleaseSid(channel->id());
       }
+      // Since this method is triggered by a signal from the DataChannel,
+      // we can't free it directly here; we need to free it asynchronously.
+      sctp_data_channels_to_free_.push_back(*it);

[pthatcher1, 2015/12/11 02:55:01]

We should probably add a RTC_DCHECK(signaling_thread()->IsCurrent()) to this
method.

[Taylor Brandstetter, 2015/12/11 18:21:48]

Done.

       sctp_data_channels_.erase(it);
+      signaling_thread()->Post(this, MSG_FREE_DATACHANNELS, nullptr);
       return;
     }
   }