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

tools/perf/measurements/rasterize_and_record.py

 # Copyright (c) 2012 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 time
 
 from metrics import smoothness
 from telemetry.page import page_measurement
 
 class StatsCollector(object):
@@ skipping 130 matching lines @@
     # first frame requested has more variance in the number of pixels
     # rasterized.
     tab.ExecuteJavaScript("""
         window.__rafFired = false;
         window.webkitRequestAnimationFrame(function() {
           chrome.gpuBenchmarking.setNeedsDisplayOnAllLayers();
           window.__rafFired  = true;
         });
     """)
 
-    tab.browser.StartTracing('webkit,webkit.console,benchmark', 60)
+    tab.browser.StartTracing('webkit.console,benchmark', 60)
     self._metrics.Start()
 
     tab.ExecuteJavaScript("""
         console.time("measureNextFrame");
         window.__rafFired = false;
         window.webkitRequestAnimationFrame(function() {
           chrome.gpuBenchmarking.setNeedsDisplayOnAllLayers();
           window.__rafFired  = true;
         });
     """)
     # Wait until the frame was drawn.
     # Needs to be adjusted for every device and for different
     # raster_record_repeat counts.
     # TODO(ernstm): replace by call-back.
     time.sleep(float(self.options.stop_wait_time))
     tab.ExecuteJavaScript('console.timeEnd("measureNextFrame")')
 
-    tab.browser.StopTracing()
+    timeline = tab.browser.StopTracing().AsTimelineModel()

[tonyg, 2013/09/12 00:49:55]

I suspect this line might be a little expensive which is why we bothered to
self._metrics.Stop() before AsTimelineModel().

Suggest flipping the order of this and the next line.

[ernstm, 2013/09/12 18:06:07]

Done.

     self._metrics.Stop()
 
-    timeline = tab.browser.GetTraceResultAndReset().AsTimelineModel()
     collector = StatsCollector(timeline)
     collector.GatherRenderingStats()
 
     rendering_stats = self._metrics.end_values
 
     results.Add('best_rasterize_time', 'seconds',
                 collector.total_best_rasterize_time / 1.e3,
                 data_type='unimportant')
     results.Add('best_record_time', 'seconds',
                 collector.total_best_record_time / 1.e3,
                 data_type='unimportant')
     results.Add('total_pixels_rasterized', 'pixels',
                 collector.total_pixels_rasterized,
                 data_type='unimportant')
     results.Add('total_pixels_recorded', 'pixels',
                 collector.total_pixels_recorded,
                 data_type='unimportant')
 
     if self.options.report_all_results:
       for k, v in rendering_stats.iteritems():
         results.Add(k, '', v)