Reland of: Improving the fake clock and using it to fix a flaky STUN timeout test.

When the fake clock's time is advanced, it now ensures all pending
queued messages have been dispatched. This allows us to write a
"SIMULATED_WAIT" macro that ticks the simulated clock by milliseconds up
until the target time.

Useful in this case, where we know the STUN timeout should take a total
of 9500ms, but it would be overly complex to write test code that waits
for each individual timeout, ensures a STUN packet has been
retransmited, etc.

(The test described above *should* be written, but it belongs in
p2ptransportchannel_unittest.cc, not webrtcsession_unittest.cc).

Review-Url: https://codereview.webrtc.org/2024813004
Cr-Commit-Position: refs/heads/master@{#13052}
diff --git a/webrtc/base/messagequeue.h b/webrtc/base/messagequeue.h
index 3a5226c..bf11037 100644
--- a/webrtc/base/messagequeue.h
+++ b/webrtc/base/messagequeue.h
@@ -37,7 +37,7 @@
 
 // MessageQueueManager does cleanup of of message queues
 
-class MessageQueueManager : public MessageHandler {
+class MessageQueueManager {
  public:
   static void Add(MessageQueue *message_queue);
   static void Remove(MessageQueue *message_queue);
@@ -50,21 +50,20 @@
   static bool IsInitialized();
 
   // Mainly for testing purposes, for use with a simulated clock.
-  // Posts a no-op event on all message queues so they will wake from the
-  // socket server select() and process messages again.
-  static void WakeAllMessageQueues();
+  // Ensures that all message queues have processed delayed messages
+  // up until the current point in time.
+  static void ProcessAllMessageQueues();
 
  private:
   static MessageQueueManager* Instance();
 
   MessageQueueManager();
-  ~MessageQueueManager() override;
+  ~MessageQueueManager();
 
   void AddInternal(MessageQueue *message_queue);
   void RemoveInternal(MessageQueue *message_queue);
   void ClearInternal(MessageHandler *handler);
-  void WakeAllMessageQueuesInternal();
-  void OnMessage(Message* pmsg) override;
+  void ProcessAllMessageQueuesInternal();
 
   static MessageQueueManager* instance_;
   // This list contains all live MessageQueues.