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

tools/profile_chrome/main.py

Index: tools/profile_chrome/main.py
diff --git a/tools/profile_chrome/main.py b/tools/profile_chrome/main.py
index 1dbf08a60d9e98cf67ca6f21cebc369988aaf689..1e3bd21348df0632f8383d10871ffaa4b102e0a5 100755
--- a/tools/profile_chrome/main.py
+++ b/tools/profile_chrome/main.py
@@ -74,6 +74,11 @@ def _CreateOptionParser():
                                  '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',
@@ -180,6 +185,10 @@ When in doubt, just try out --trace-frame-viewer.
   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 = []
@@ -210,8 +219,9 @@ When in doubt, just try out --trace-frame-viewer.
         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)
@@ -223,19 +233,23 @@ When in doubt, just try out --trace-frame-viewer.
                     'Chrome tracing results in duplicate trace events.')
 
   enabled_controllers = []
-  if chrome_categories:
-    enabled_controllers.append(
-        chrome_controller.ChromeTracingController(device,
-                                                  package_info,
-                                                  chrome_categories,
-                                                  options.ring_buffer,
-                                                  options.trace_memory))
+  # 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,
+                                                  options.startup))
   if perf_categories:
     enabled_controllers.append(
         perf_controller.PerfProfilerController(device,
@@ -249,7 +263,7 @@ When in doubt, just try out --trace-frame-viewer.
     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)