Add cleanup for measurements that use tracing

tools/perf/measurements/loading_trace.py

 # Copyright 2013 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 metrics import loading
 from metrics import timeline
 from telemetry.page import page_measurement
 
 class LoadingTrace(page_measurement.PageMeasurement):
   def __init__(self, *args, **kwargs):
     super(LoadingTrace, self).__init__(*args, **kwargs)
@@ skipping 10 matching lines @@
     # In current telemetry tests, all tests wait for DocumentComplete state,
     # but we need to wait for the load event.
     tab.WaitForJavaScriptExpression('performance.timing.loadEventStart', 300)
 
     # TODO(nduca): when crbug.com/168431 is fixed, modify the page sets to
     # recognize loading as a toplevel action.
     self._timeline_metric.Stop(page, tab)
 
     loading.LoadingMetric().AddResults(tab, results)
     self._timeline_metric.AddResults(tab, results)
+
+  def CleanUpAfterPage(self, _, tab):
+    self._timeline_metric.CleanUp(tab)