Revert of Make sure that tracing is always cleaned up for v8_gc_times page_test (patchset #4 id:60001 of https://codereview.chromium.org/1151933005/)

Reason for revert:
I suspect this is causing failures on telemetry_perf_unittests - see https://build.chromium.org/p/chromium.win/builders/XP%20Tests%20%281%29 build #37836 and later

Original issue's description:
> Make sure that tracing is always cleaned up for v8_gc_times page_test
>
> BUG=491104
> CQ_EXTRA_TRYBOTS=tryserver.chromium.perf:linux_perf_bisect;tryserver.chromium.perf:mac_perf_bisect;tryserver.chromium.perf:win_perf_bisect;tryserver.chromium.perf:android_nexus5_perf_bisect
>
> Committed: https://crrev.com/1d1d10c687de9424db5a66a89d179f11784d7ee8
> Cr-Commit-Position: refs/heads/master@{#331590}

TBR=sullivan@chromium.org,rmcilroy@chromium.org,prasadv@chromium.org,nednguyen@google.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=491104

Review URL: https://codereview.chromium.org/1147093008

Cr-Commit-Position: refs/heads/master@{#331669}

tools/perf/measurements/v8_gc_times.py

@@ -42,10 +42,6 @@ class V8GCTimes(page_test.PageTest):
     renderer_process = timeline_model.GetRendererProcessFromTabId(tab.id)
     self._AddV8MetricsToResults(renderer_process, results)
 
-  def CleanUpAfterPage(self, page, tab):
-    if tab.browser.platform.tracing_controller.is_tracing_running:
-      tab.browser.platform.tracing_controller.Stop()
-
   def _AddV8MetricsToResults(self, process, results):
     if process is None:
       return

tools/perf/measurements/v8_gc_times_unittest.py

@@ -238,9 +238,6 @@ class V8GCTimesTests(page_test_test_case.PageTestTestCase):
           'Result for [' + key + '] - expected ' + str(expected[key]) +
           ' but got ' + str(actual[key]))
 
-  def testCleanUpTrace(self):
-    self.TestTracingCleanedUp(v8_gc_times.V8GCTimes, self._options)
-
 
 def _ActualValues(results):
   return dict(list(

tools/telemetry/telemetry/unittest_util/page_test_test_case.py

@@ -87,7 +87,7 @@ class PageTestTestCase(unittest.TestCase):
           ActualStartTracing(*args, **kwargs)
           start_tracing_called[0] = True
           raise exceptions.IntentionalException
-        browser.platform.tracing_controller.Start = FakeStartTracing
+        browser.StartTracing = FakeStartTracing
 
         ActualStopTracing = browser.platform.tracing_controller.Stop
         def FakeStopTracing(*args, **kwargs):
@@ -101,7 +101,7 @@ class PageTestTestCase(unittest.TestCase):
     measurement = BuggyMeasurement()
     try:
       self.RunMeasurement(measurement, ps, options=options)
-    except page_test.MultiTabTestAppCrashError:
+    except page_test.TestNotSupportedOnPlatformError:
       pass
     if start_tracing_called[0]:
       self.assertTrue(stop_tracing_called[0])