Close 'accepted' sockets when listening socket is closed. Fixes raw_server_socket_cancel_test.

runtime/bin/eventhandler_win.cc

Index: runtime/bin/eventhandler_win.cc
diff --git a/runtime/bin/eventhandler_win.cc b/runtime/bin/eventhandler_win.cc
index fc0522a3dc3c1a399f771ccdf256727f7e4edd3f..f6e91c43692a8ed2189b0c14319fdea8a9417895 100644
--- a/runtime/bin/eventhandler_win.cc
+++ b/runtime/bin/eventhandler_win.cc
@@ -435,6 +435,9 @@ void ListenSocket::AcceptComplete(IOBuffer* buffer, HANDLE completion_port) {
       Log::PrintErr("setsockopt failed: %d\n", WSAGetLastError());
       closesocket(buffer->client());
     }
+  } else {
+    // Close the socket, as it's already accepted.
+    closesocket(buffer->client());
   }
 
   pending_accept_count_--;