Add a --startup option to generate combined traces for startup.

tools/profile_chrome/main.py

 #!/usr/bin/env python
 #
 # 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 logging
 import optparse
 import os
 import sys
@@ skipping 56 matching lines @@
   return callback
 
 
 def _CreateOptionParser():
   parser = optparse.OptionParser(description='Record about://tracing profiles '
                                  'from Android browsers. See http://dev.'
                                  'chromium.org/developers/how-tos/trace-event-'
                                  'profiling-tool for detailed instructions for '
                                  'profiling.')
 
+  parser.add_option('--startup', help='Trace Chrome Startup. Possible values '
+                    'are "warm" and "cold". Cold start is done with the page '

[pasko, 2015/01/27 12:59:00]

nit: maybe rephrase:
The "warm" does not perform special steps, while the "cold" flushes the OS page
cache before start.

[Benoit L, 2015/01/27 13:50:26]

Done.

+                    'cache flushed before, warm without. Note that "cold" '
+                    'requires a device with root access.', default=None)
+
   timed_options = optparse.OptionGroup(parser, 'Timed tracing')
   timed_options.add_option('-t', '--time', help='Profile for N seconds and '
                           'download the resulting trace.', metavar='N',
                            type='float')
   parser.add_option_group(timed_options)
 
   cont_options = optparse.OptionGroup(parser, 'Continuous tracing')
   cont_options.add_option('--continuous', help='Profile continuously until '
                           'stopped.', action='store_true')
   cont_options.add_option('--ring-buffer', help='Use the trace buffer as a '
@@ skipping 86 matching lines @@
 
   if options.verbose:
     logging.getLogger().setLevel(logging.DEBUG)
 
   devices = android_commands.GetAttachedDevices()
   if len(devices) != 1:
     parser.error('Exactly 1 device must be attached.')
   device = device_utils.DeviceUtils(devices[0])
   package_info = profiler.GetSupportedBrowsers()[options.browser]
 
+  if options.startup and options.startup not in ['cold', 'warm']:

[Sami, 2015/01/27 13:15:47]

Could you use optparser's "choices" mechanism to let it validate this
automatically?

[Benoit L, 2015/01/27 13:50:25]

Didn't know about this mechanism. Thank you !
Done.

+    ui.PrintMessage('Startup mode should be one of ["cold", "warm"]')
+    return 1
+
   if options.chrome_categories in ['list', 'help']:
     ui.PrintMessage('Collecting record categories list...', eol='')
     record_categories = []
     disabled_by_default_categories = []
     record_categories, disabled_by_default_categories = \
         chrome_controller.ChromeTracingController.GetCategories(
             device, package_info)
 
     ui.PrintMessage('done')
     ui.PrintMessage('Record Categories:')
@@ skipping 10 matching lines @@
     ui.PrintMessage('\n'.join(
         systrace_controller.SystraceController.GetCategories(device)))
     return 0
 
   if (perf_controller.PerfProfilerController.IsSupported() and
       options.perf_categories in ['list', 'help']):
     ui.PrintMessage('\n'.join(
         perf_controller.PerfProfilerController.GetCategories(device)))
     return 0
 
-  if not options.time and not options.continuous:
-    ui.PrintMessage('Time interval or continuous tracing should be specified.')
+  if not options.time and not options.continuous and not options.startup:
+    ui.PrintMessage('Time interval, continuous or startup tracing should be '
+                    'specified.')
     return 1
 
   chrome_categories = _ComputeChromeCategories(options)
   systrace_categories = _ComputeSystraceCategories(options)
   perf_categories = _ComputePerfCategories(options)
 
   if chrome_categories and 'webview' in systrace_categories:
     logging.warning('Using the "webview" category in systrace together with '
                     'Chrome tracing results in duplicate trace events.')
 
   enabled_controllers = []
+  # Systrace need to be put first, because when we profile startup, we want to

[pasko, 2015/01/27 12:59:00]

nit: we usually try to avoid 'we' in the comments.
nit: the comment would be more readable if you explain the final state rather
than the change you are making. Like:
# Enable the systrace and chrome controller. The systrace controller should go
# first because it provides early events used in the chrome controller.

[Benoit L, 2015/01/27 13:50:26]

Done.

+  # see events from the start of execution, which is initiated in the chrome
+  # controller.
+  if systrace_categories:
+    enabled_controllers.append(
+        systrace_controller.SystraceController(device,
+                                               systrace_categories,
+                                               options.ring_buffer))
+
   if chrome_categories:
     enabled_controllers.append(
         chrome_controller.ChromeTracingController(device,
                                                   package_info,
                                                   chrome_categories,
                                                   options.ring_buffer,
-                                                  options.trace_memory))
-  if systrace_categories:
-    enabled_controllers.append(
-        systrace_controller.SystraceController(device,
-                                               systrace_categories,
-                                               options.ring_buffer))
-
+                                                  options.trace_memory,
+                                                  options.startup))
   if perf_categories:
     enabled_controllers.append(
         perf_controller.PerfProfilerController(device,
                                                perf_categories))
 
   if not enabled_controllers:
     ui.PrintMessage('No trace categories enabled.')
     return 1
 
   if options.output:
     options.output = os.path.expanduser(options.output)
   result = profiler.CaptureProfile(
       enabled_controllers,
-      options.time if not options.continuous else 0,
+      options.time if options.time else 0,

[Sami, 2015/01/27 13:15:47]

Why this change?

[Benoit L, 2015/01/27 13:50:26]

Because options.time is None when options.continuous or options.startup is
specified.

       output=options.output,
       compress=options.compress,
       write_json=options.json)
   if options.view:
     if sys.platform == 'darwin':
       os.system('/usr/bin/open %s' % os.path.abspath(result))
     else:
       webbrowser.open(result)