Mojo EDK: Add tests to exercise races in handle transit

mojo/edk/system/data_pipe_producer_dispatcher.cc

Index: mojo/edk/system/data_pipe_producer_dispatcher.cc
diff --git a/mojo/edk/system/data_pipe_producer_dispatcher.cc b/mojo/edk/system/data_pipe_producer_dispatcher.cc
index d056e7dbc8331962cc56c50b630db5125f632b7d..5c7b75df76665e439a1d528136c593ce100d4578 100644
--- a/mojo/edk/system/data_pipe_producer_dispatcher.cc
+++ b/mojo/edk/system/data_pipe_producer_dispatcher.cc
@@ -403,6 +403,7 @@ DataPipeProducerDispatcher::Deserialize(const void* data,
     dispatcher->available_capacity_ = state->available_capacity;
     dispatcher->peer_closed_ = state->flags & kFlagPeerClosed;
     dispatcher->InitializeNoLock();
+    dispatcher->UpdateSignalsStateNoLock();
   }
 
   return dispatcher;