Bug 1521304: Move some Mutexes r=tuexen,dminor

netwerk/sctp/datachannel/DataChannel.cpp

@@ -2312,13 +2312,22 @@ int DataChannelConnection::ReceiveCallback(struct socket *sock, void *data,
 
   if (!data) {
     LOG(("ReceiveCallback: SCTP has finished shutting down"));
+  } else {
+    bool locked = false;
+    if (!IsSTSThread()) {
+      mLock.Lock();
+      locked = true;
     } else {
       mLock.AssertCurrentThreadOwns();
+    }
     if (flags & MSG_NOTIFICATION) {
       HandleNotification(static_cast<union sctp_notification *>(data), datalen);
     } else {
       HandleMessage(data, datalen, ntohl(rcv.rcv_ppid), rcv.rcv_sid, flags);
     }
+    if (locked) {
+      mLock.Unlock();
+    }
   }
   // sctp allocates 'data' with malloc(), and expects the receiver to free
   // it (presumably with free).