Introduce TracingController and TracingControllerBackend skeleton

tools/perf/measurements/thread_times.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 timeline_controller
 from metrics import timeline
-from telemetry.core.backends.chrome import tracing_backend
+from telemetry.core.platform import tracing_category_filter
 from telemetry.page import page_measurement
 
 class ThreadTimes(page_measurement.PageMeasurement):
   def __init__(self):
     super(ThreadTimes, self).__init__('RunSmoothness')
     self._timeline_controller = None
 
   @classmethod
   def AddCommandLineArgs(cls, parser):
     parser.add_option('--report-silk-results', action='store_true',
                       help='Report results relevant to silk.')
     parser.add_option('--report-silk-details', action='store_true',
                       help='Report details relevant to silk.')
 
   def WillNavigateToPage(self, page, tab):
     self._timeline_controller = timeline_controller.TimelineController()
     if self.options.report_silk_details:
       # We need the other traces in order to have any details to report.
-      self.timeline_controller.trace_categories = \
-          tracing_backend.DEFAULT_TRACE_CATEGORIES
+      self.timeline_controller.trace_categories = None
     else:
       self._timeline_controller.trace_categories = \
-          tracing_backend.MINIMAL_TRACE_CATEGORIES
+          tracing_category_filter.CreateNoOverheadFilter().filter_string
     self._timeline_controller.SetUp(page, tab)
 
   def WillRunActions(self, page, tab):
     self._timeline_controller.Start(tab)
 
   def DidRunActions(self, page, tab):
     self._timeline_controller.Stop(tab)
 
   def MeasurePage(self, page, tab, results):
     metric = timeline.ThreadTimesTimelineMetric()
     renderer_thread = \
         self._timeline_controller.model.GetRendererThreadFromTabId(tab.id)
     if self.options.report_silk_results:
       metric.results_to_report = timeline.ReportSilkResults
     if self.options.report_silk_details:
       metric.details_to_report = timeline.ReportSilkDetails
     metric.AddResults(self._timeline_controller.model, renderer_thread,
                       self._timeline_controller.smooth_records, results)
 
   def CleanUpAfterPage(self, _, tab):
     self._timeline_controller.CleanUp(tab)