mojo: Allow basic RunLoop to be quit from a posted task.

mojo/python/tests/async_wait_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 unittest
 
 # pylint: disable=F0401
 import mojo.embedder
 from mojo import system
 
 
 class AsyncWaitTest(unittest.TestCase):
 
   def setUp(self):
     mojo.embedder.Init()
     self.loop = system.RunLoop()
     self.array = []
     self.handles = system.MessagePipe()
     self.cancel = self.handles.handle0.AsyncWait(system.HANDLE_SIGNAL_READABLE,
                                                  system.DEADLINE_INDEFINITE,
-                                                 self.OnResult)
-    self.loop.PostDelayedTask(self.WriteToHandle, 100)
+                                                 self._OnResult)
 
   def tearDown(self):
+    self.cancel()
     self.handles = None
     self.array = None
     self.loop = None
 
-  def OnResult(self, value):
+  def _OnResult(self, value):
     self.array.append(value)
 
-  def WriteToHandle(self):
+  def _WriteToHandle(self):
     self.handles.handle1.WriteMessage()
 
+  def _PostWriteAndRun(self):
+    self.loop.PostDelayedTask(self._WriteToHandle, 0)
+    self.loop.RunUntilIdle()
+
   def testAsyncWait(self):
-    self.loop.RunUntilIdle()
+    self._PostWriteAndRun()
     self.assertEquals(len(self.array), 1)
     self.assertEquals(system.RESULT_OK, self.array[0])
-    self.cancel()
 
   def testAsyncWaitCancel(self):
-    self.loop.PostDelayedTask(self.cancel, 50)
-    self.loop.RunUntilIdle()
+    self.loop.PostDelayedTask(self.cancel, 0)
+    self._PostWriteAndRun()
     self.assertEquals(len(self.array), 0)
-    self.cancel()
 
   def testAsyncWaitImmediateCancel(self):
     self.cancel()
-    self.loop.RunUntilIdle()
+    self._PostWriteAndRun()
     self.assertEquals(len(self.array), 0)
-    self.cancel()