Setting --run-python-script flag for runtest.py invocation.

scripts/slave/recipe_modules/bisect_tester/perf_test.py

 # Copyright 2015 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 os
 import re
 import time
 
 from . import parse_metric
 
@@ skipping 181 matching lines @@
   command_parts = command.split()
   stdout = api.m.raw_io.output()
   stderr = api.m.raw_io.output()
 
   # TODO(prasadv): Remove this once bisect runs are no longer running
   # against revisions from February 2016 or earlier.
   kwargs = {}
   if 'android-chrome' in command:  # pragma: no cover
     kwargs['env'] = {'CHROMIUM_OUTPUT_DIR': api.m.chromium.output_dir}
 
+  run_python_command = False
+  if command_parts[0].startswith('python'):  # pragma: no cover
+    # Handling case when dashboard sends python as the command (for windows).
+    command_parts = command_parts[1:]
+    run_python_command = True
+  elif _is_telemetry_command(command):
+    run_python_command = True

[sullivan, 2016/04/25 18:43:12]

The code could use some more comments explaining exactly what's going on:

1) We need this python_mode=True and need to strip 'python' out of the command
for runtest.py? Are more details available about why?

2) The dashboard sends 'python' as the command: why do we handle that case here
instead of change the dashboard?

3) Why do we check command_parts[0].startswith('python') and then drop the
entire thing if it does? Could it be anything other than 'python'? If it could,
what are we dropping?

4) Why do we effectively have two names for what appears to be telling
run_test.py to prepend 'python ' to the command (run_python_command and
python_mode)?

[RobertoCN, 2016/04/25 19:34:31]

Done.

   try:
     step_result = api.m.chromium.runtest(
         test=_rebase_path(command_parts[0]),
         args=command_parts[1:],
         xvfb=True,
         name=step_name,
+        python_mode=run_python_command,
         stdout=stdout,
         stderr=stderr,
         **kwargs)
     step_result.presentation.logs['Captured Output'] = (
         step_result.stdout or '').splitlines()
   except api.m.step.StepFailure as sf:
     sf.result.presentation.logs['Failure Output'] = (
         sf.result.stdout or '').splitlines()
     if sf.result.stderr:  # pragma: no cover
       sf.result.presentation.logs['stderr'] = (
         sf.result.stderr).splitlines()
     return sf.result.stdout, sf.result.stderr, sf.result.retcode
   return step_result.stdout, step_result.stderr, step_result.retcode