CC: Add 'cc-benchmark' traces for minimal tracing in benchmarks.

tools/perf/metrics/timeline.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.
 import collections
 import itertools
 
 from metrics import Metric
 from telemetry.core.timeline import bounds
 from telemetry.page import page_measurement
 
 TRACING_MODE = 'tracing-mode'
 TIMELINE_MODE = 'timeline-mode'
 
+# All tracing categories not disabled-by-default
+DEFAULT_TRACE_CATEGORIES = None
+
+# Categories for absolute minimum overhead tracing. This contains no
+# sub-traces of thread tasks, so it's only useful for capturing the
+# cpu-time spent on threads (as well as needed benchmark traces)
+MINIMAL_TRACE_CATEGORIES = ("toplevel,"
+                            "benchmark,"
+                            "cc-benchmark,"
+                            "webkit.console,"
+                            "trace_event_overhead")
+
 
 class MissingFramesError(page_measurement.MeasurementFailure):
   def __init__(self):
     super(MissingFramesError, self).__init__(
         'No frames found in trace. Unable to normalize results.')
 
 
 class TimelineMetric(Metric):
   def __init__(self, mode):
     """ Initializes a TimelineMetric object.
     """
     super(TimelineMetric, self).__init__()
     assert mode in (TRACING_MODE, TIMELINE_MODE)
+    self.trace_categories = DEFAULT_TRACE_CATEGORIES
     self._mode = mode
     self._model = None
     self._renderer_process = None
     self._actions = []
     self._action_ranges = []
 
   def Start(self, page, tab):
     """Starts gathering timeline data.
 
     mode: TRACING_MODE or TIMELINE_MODE
     """
     self._model = None
     if self._mode == TRACING_MODE:
       if not tab.browser.supports_tracing:
         raise Exception('Not supported')
-      tab.browser.StartTracing()
+      tab.browser.StartTracing(self.trace_categories)
     else:
       assert self._mode == TIMELINE_MODE
       tab.StartTimelineRecording()
 
   def Stop(self, page, tab):
     if self._mode == TRACING_MODE:
       trace_result = tab.browser.StopTracing()
       self._model = trace_result.AsTimelineModel()
       self._renderer_process = self._model.GetRendererProcessFromTab(tab)
       self._action_ranges = [ action.GetActiveRangeOnTimeline(self._model)
@@ skipping 223 matching lines @@
     idle_time_result = (float(idle_time) / num_frames) if num_frames else 0
     results.Add(ThreadDetailResultName(self.name, "idle"),
                 'ms', idle_time_result)
 
 
 class ThreadTimesTimelineMetric(TimelineMetric):
   def __init__(self):
     super(ThreadTimesTimelineMetric, self).__init__(TRACING_MODE)
     self.results_to_report = AllThreads
     self.details_to_report = NoThreads
+    self.trace_categories = MINIMAL_TRACE_CATEGORIES
 
   def CountSlices(self, slices, substring):
     count = 0
     for event in slices:
       if substring in event.name:
         count += 1
     return count
 
   def AddResults(self, tab, results):
     # We need at least one action or we won't count any slices.
@@ skipping 25 matching lines @@
     num_frames = self.CountSlices(frame_slices, FrameTraceName)
 
     # Report the desired results and details.
     for thread_results in thread_category_results.values():
       if thread_results.name in self.results_to_report:
         thread_results.AddResults(num_frames, results)
       # TOOD(nduca): When generic results objects are done, this special case
       # can be replaced with a generic UI feature.
       if thread_results.name in self.details_to_report:
         thread_results.AddDetailedResults(num_frames, results)