Android perf tests: only store the retry results if it's better.

build/android/pylib/perf/setup.py

 # Copyright 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.
 
 """Generates test runner factory and tests for performance tests."""
 
 import json
 import fnmatch
 import logging
 import os
 import psutil
 import signal
+import shutil
 import time
 
 from pylib import android_commands
 from pylib import cmd_helper
 from pylib import constants
 from pylib import forwarder
 from pylib import ports
 
 import test_runner
 
@@ skipping 28 matching lines @@
 
 def Setup(test_options):
   """Create and return the test runner factory and tests.
 
   Args:
     test_options: A PerformanceOptions object.
 
   Returns:
     A tuple of (TestRunnerFactory, tests).
   """
-  if not os.path.exists(constants.PERF_OUTPUT_DIR):
-    os.makedirs(constants.PERF_OUTPUT_DIR)
+  if os.path.exists(constants.PERF_OUTPUT_DIR):
+    shutil.rmtree(constants.PERF_OUTPUT_DIR)
+  os.makedirs(constants.PERF_OUTPUT_DIR)
 
   # Before running the tests, kill any leftover server.
   _KillPendingServers()
 
   with file(test_options.steps, 'r') as f:
     tests = json.load(f)
 
   # The list is necessary to keep the steps order, but internally
   # the format is squashed from a list of lists into a single dict:
   # [["A", "cmd"], ["B", "cmd"]] into {"A": "cmd", "B": "cmd"}
   sorted_test_names = [i[0] for i in tests]
   tests_dict = dict(tests)
 
   if test_options.test_filter:
     sorted_test_names = fnmatch.filter(sorted_test_names,
                                        test_options.test_filter)
     tests_dict = dict((k, v) for k, v in tests_dict.iteritems()
                       if k in sorted_test_names)
 
   flaky_steps = []
   if test_options.flaky_steps:
     with file(test_options.flaky_steps, 'r') as f:
       flaky_steps = json.load(f)
 
   def TestRunnerFactory(device, shard_index):
     return test_runner.TestRunner(
         test_options, device, tests_dict, flaky_steps)
 
   return (TestRunnerFactory, sorted_test_names)