Adding MOJO_HANDLE_SIGNAL_PEER_CLOSED to be notified when a peer is closed.

mojo/edk/system/local_message_pipe_endpoint.cc

Index: mojo/edk/system/local_message_pipe_endpoint.cc
diff --git a/mojo/edk/system/local_message_pipe_endpoint.cc b/mojo/edk/system/local_message_pipe_endpoint.cc
index 124241e069e8439d578e06bf7037fd5f2be18fdc..86d241c93171a896fd7fd43980818bd82368b704 100644
--- a/mojo/edk/system/local_message_pipe_endpoint.cc
+++ b/mojo/edk/system/local_message_pipe_endpoint.cc
@@ -137,7 +137,10 @@ HandleSignalsState LocalMessagePipeEndpoint::GetHandleSignalsState() const {
     rv.satisfied_signals |= MOJO_HANDLE_SIGNAL_WRITABLE;
     rv.satisfiable_signals |=
         MOJO_HANDLE_SIGNAL_READABLE | MOJO_HANDLE_SIGNAL_WRITABLE;
+  } else {
+    rv.satisfied_signals |= MOJO_HANDLE_SIGNAL_PEER_CLOSED;
   }
+  rv.satisfiable_signals |= MOJO_HANDLE_SIGNAL_PEER_CLOSED;
   return rv;
 }