Prevent data race in MessageQueue.

webrtc/base/thread.cc

Index: webrtc/base/thread.cc
diff --git a/webrtc/base/thread.cc b/webrtc/base/thread.cc
index cda4ba475c8b6bfebd80fe994c518f4b55d3e666..725ca94efc458c8a60b4d4c27358d3104004b926 100644
--- a/webrtc/base/thread.cc
+++ b/webrtc/base/thread.cc
@@ -353,8 +353,10 @@ void Thread::Send(MessageHandler* phandler, uint32_t id, MessageData* pdata) {
   }
 
   // Wait for a reply
-
-  ss_->WakeUp();
+  {
+    SharedScope ss(&ss_lock_);
+    ss_->WakeUp();

[pthatcher1, 2016/02/12 00:16:33]

Instead of making ss_lock_ protected, could we just call
socketserver()->WakeUp() here?

[joachim, 2016/02/12 15:09:52]

That would still be racy imho because the variable would not be locked between
the return of the socketserver() and the invokation of "WakeUp". Instead I
introduced a method "WakeUpSocketServer()" in MessageQueue that takes care of
proper locking.

With that, the socket server related properties can be made private in
MessageQueue.

+  }
 
   bool waited = false;
   crit_.Enter();