Add cleanup for measurements that use tracing

tools/perf/measurements/thread_times_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.
 from measurements import thread_times
 from telemetry.core import wpr_modes
 from telemetry.page import page_measurement_unittest_base
 from telemetry.unittest import options_for_unittests
 from metrics import timeline
 
 class ThreadTimesUnitTest(
       page_measurement_unittest_base.PageMeasurementUnitTestBase):
   def setUp(self):
     self._options = options_for_unittests.GetCopy()
     self._options.browser_options.wpr_mode = wpr_modes.WPR_OFF
 
   def testBasic(self):
     ps = self.CreatePageSetFromFileInUnittestDataDir('scrollable_page.html')
     measurement = thread_times.ThreadTimes()
     timeline_options = self._options
     results = self.RunMeasurement(measurement, ps, options = timeline_options)
     self.assertEquals(0, len(results.failures))
 
     for category in timeline.TimelineThreadCategories.values():
       cpu_time_name = timeline.ThreadCpuTimeResultName(category)
       cpu_time = results.FindAllPageSpecificValuesNamed(cpu_time_name)
       self.assertEquals(len(cpu_time), 1)
+
+  def testCleanUpTrace(self):
+    self.TestTracingCleanedUp(thread_times.ThreadTimes, self._options)