Adding MOJO_HANDLE_SIGNAL_PEER_CLOSED to be notified when a peer is closed.

mojo/python/tests/system_unittest.py

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import random
 import time
 
 import mojo_unittest
 
 # pylint: disable=E0611
@@ skipping 27 matching lines @@
     self.assertLess(system.RESULT_UNAVAILABLE, 0)
     self.assertLess(system.RESULT_DATA_LOSS, 0)
     self.assertLess(system.RESULT_BUSY, 0)
     self.assertLess(system.RESULT_SHOULD_WAIT, 0)
 
   def testConstants(self):
     self.assertGreaterEqual(system.DEADLINE_INDEFINITE, 0)
     self.assertGreaterEqual(system.HANDLE_SIGNAL_NONE, 0)
     self.assertGreaterEqual(system.HANDLE_SIGNAL_READABLE, 0)
     self.assertGreaterEqual(system.HANDLE_SIGNAL_WRITABLE, 0)
+    self.assertGreaterEqual(system.HANDLE_SIGNAL_PEER_CLOSED, 0)
     self.assertGreaterEqual(system.WRITE_MESSAGE_FLAG_NONE, 0)
     self.assertGreaterEqual(system.READ_MESSAGE_FLAG_NONE, 0)
     self.assertGreaterEqual(system.READ_MESSAGE_FLAG_MAY_DISCARD, 0)
     self.assertGreaterEqual(system.WRITE_DATA_FLAG_NONE, 0)
     self.assertGreaterEqual(system.WRITE_DATA_FLAG_ALL_OR_NONE, 0)
     self.assertGreaterEqual(system.READ_DATA_FLAG_NONE, 0)
     self.assertGreaterEqual(system.READ_DATA_FLAG_ALL_OR_NONE, 0)
     self.assertGreaterEqual(system.READ_DATA_FLAG_DISCARD, 0)
     self.assertGreaterEqual(system.READ_DATA_FLAG_QUERY, 0)
     self.assertGreaterEqual(system.READ_DATA_FLAG_PEEK, 0)
@@ skipping 230 matching lines @@
     self.assertEquals(system.RESULT_OK, res1)
     self.assertEquals(system.RESULT_OK, res2)
     self.assertEquals(DATA_SIZE, len(buf1.buffer))
     self.assertEquals(DATA_SIZE, len(buf2.buffer))
     self.assertEquals(buf1.buffer, buf2.buffer)
 
     buf1.buffer[:] = data
     self.assertEquals(data, buf1.buffer)
     self.assertEquals(data, buf2.buffer)
     self.assertEquals(buf1.buffer, buf2.buffer)