[Telemetry] Add tracing_agent API.

tools/perf/measurements/smoothness_unittest.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.
 import sys
 
 from measurements import smoothness
 from metrics import power
 from telemetry import decorators
 from telemetry.core import exceptions
 from telemetry.core import wpr_modes
 from telemetry.page import page
 from telemetry.unittest_util import options_for_unittests
 from telemetry.unittest_util import page_test_test_case
 
 class FakeTracingController(object):
   def __init__(self):
     self.category_filter = None
   def Start(self, _options, category_filter, _timeout):
     self.category_filter = category_filter
-  def IsDisplayTracingSupported(self):
-    return False
 
 class FakePlatform(object):
   def __init__(self):
     self.tracing_controller = FakeTracingController()
   def CanMonitorPower(self):
     return False
 
 
 class FakeBrowser(object):
   def __init__(self):
@@ skipping 163 matching lines @@
         self.fake_power = self._power_metric = FakePowerMetric(platform)
 
     measurement = BuggyMeasurement()
     try:
       self.RunMeasurement(measurement, ps)
     except exceptions.IntentionalException:
       pass
 
     self.assertTrue(measurement.fake_power.start_called)
     self.assertTrue(measurement.fake_power.stop_called)