telemetry: Make trace profiler work with trace-based benchmarks.

tools/perf/measurements/smoothness.py

 # Copyright (c) 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 smoothness
 from metrics.gpu_rendering_stats import GpuRenderingStats
 from telemetry.page import page_measurement
 
 
 class DidNotScrollException(page_measurement.MeasurementFailure):
@@ skipping 25 matching lines @@
 
   def CustomizeBrowserOptions(self, options):
     smoothness.SmoothnessMetrics.CustomizeBrowserOptions(options)
     if self.force_enable_threaded_compositing:
       options.AppendExtraBrowserArgs('--enable-threaded-compositing')
 
   def CanRunForPage(self, page):
     return hasattr(page, 'smoothness')
 
   def WillRunAction(self, page, tab, action):
-    # TODO(ernstm): remove 'webkit' category when
-    # https://codereview.chromium.org/23848006/ has landed.
-    tab.browser.StartTracing('webkit,webkit.console,benchmark', 60)
+    # We don't need to start tracing, if a trace profiler is already running.
+    # Note that all trace event categories are enabled in this case, which
+    # increases the risk of a trace buffer overflow.
+    if self.options.profiler != 'trace':
+      tab.browser.StartTracing('webkit.console,benchmark', 60)
     if tab.browser.platform.IsRawDisplayFrameRateSupported():
       tab.browser.platform.StartRawDisplayFrameRateMeasurement()
     self._metrics = smoothness.SmoothnessMetrics(tab)
     if action.CanBeBound():
       self._metrics.BindToAction(action)
     else:
       self._metrics.Start()
 
   def DidRunAction(self, page, tab, action):
     if tab.browser.platform.IsRawDisplayFrameRateSupported():
       tab.browser.platform.StopRawDisplayFrameRateMeasurement()
     if not action.CanBeBound():
       self._metrics.Stop()
+    # Always stop tracing at this point. If a trace profiler is running, it will
+    # be stopped here.
     tab.browser.StopTracing()
 
   def FindTimelineMarker(self, timeline):
     events = [s for
               s in timeline.GetAllEventsOfName(
                   smoothness.TIMELINE_MARKER)
               if s.parent_slice == None]
     if len(events) != 1:
       raise MissingTimelineMarker()
     return events[0]
 
   def MeasurePage(self, page, tab, results):
     rendering_stats_deltas = self._metrics.deltas
 
     if not (rendering_stats_deltas['numFramesSentToScreen'] > 0):
       raise DidNotScrollException()
 
     loading.LoadingMetric().AddResults(tab, results)
 
     smoothness.CalcFirstPaintTimeResults(results, tab)
 
-    timeline = tab.browser.GetTraceResultAndReset().AsTimelineModel()
+    # Fetch the results without resetting, if a trace profiler is running. The
+    # profiler needs to read the results later on.
+    if self.options.profiler == 'trace':
+      timeline = tab.browser.GetTraceResult().AsTimelineModel()
+    else:
+      timeline = tab.browser.GetTraceResultAndReset().AsTimelineModel()
     timeline_marker = self.FindTimelineMarker(timeline)
     benchmark_stats = GpuRenderingStats(timeline_marker,
                                         rendering_stats_deltas,
                                         self._metrics.is_using_gpu_benchmarking)
     smoothness.CalcResults(benchmark_stats, results)
 
     if self.options.report_all_results:
       for k, v in rendering_stats_deltas.iteritems():
         results.Add(k, '', v)
 
     if tab.browser.platform.IsRawDisplayFrameRateSupported():
       for r in tab.browser.platform.GetRawDisplayFrameRateMeasurements():
         if r.value is None:
           raise MissingDisplayFrameRate(r.name)
         results.Add(r.name, r.unit, r.value)