Remove build directory before performing perf tryjob.

scripts/slave/recipe_modules/perf_try/api.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.
 
 """API for the perf try job recipe module.
 
 This API is meant to enable the perf try job recipe on any chromium-supported
 platform for any test that can be run via buildbot, perf or otherwise.
 """
 
@@ skipping 165 matching lines @@
     compile_targets = self.m.chromium_tests.get_compile_targets(
         bot_config, bot_db, tests=[])
     if self.m.chromium.c.TARGET_PLATFORM == 'android':
       self.m.chromium_android.clean_local_files()
       compile_targets = None
     else:
       # Removes any chrome temporary files or build.dead directories.
       self.m.chromium.cleanup_temp()
 
     if 'With Patch' in name:
+      # We've had some cases where a stale build directory was used on perf try job,
+      # leading to unwanted cache and temp data. The best way to ensure
+      # the old build directory is removed before doing any compilation.
+      self.m.file.rmtree(
+        'build directory',
+        self.m.chromium.c.build_dir.join(self.m.chromium.c.build_config_fs))
+
       self.m.chromium_tests.transient_check(
           update_step,
           lambda transform_name: self.m.chromium_tests.run_mb_and_compile(
               compile_targets, None, name_suffix=transform_name('')))
     else:
       self.m.chromium_tests.run_mb_and_compile(
           compile_targets, None, name_suffix=' %s' % name)
 
   def _run_test(self, cfg, **kwargs):
     """Runs test from config and return results."""
     values, overall_output, retcodes = self.m.bisect_tester.run_test(
         cfg, **kwargs)
     all_values = self.m.bisect_tester.digest_run_results(values, retcodes, cfg)
     overall_success = True
     if (not kwargs.get('allow_flakes', True) and
         cfg.get('test_type', 'perf') != 'return_code'):
       overall_success = all(v == 0 for v in retcodes)
-    if not overall_success:  # pragma: no cover

[RobertoCN, 2016/03/07 22:24:40]

Not raising an exception and instead returning the overall_success as a ret_code
make sense to me. However, I don't see how it's related to the removal of the
build directory.

We could at least add a note in the CL description saying why we are doing this.

-      raise self.m.step.StepFailure(
-          'Patched version failed to run performance test.')
     return {
         'results': all_values,
         'ret_code': overall_success,
         'output': ''.join(overall_output)
     }
 
   def _build_and_run_tests(self, cfg, update_step, bot_db, revision,
                            **kwargs):
     """Compiles binaries and runs tests for a given a revision."""
     update_step = self._checkout_revision(update_step, bot_db, revision)
@@ skipping 291 matching lines @@
 
 def _prepend_src_to_path_in_command(test_cfg):
   command_to_run = []
   for v in test_cfg.get('command').split():
     if v in ['./tools/perf/run_benchmark',
              'tools/perf/run_benchmark',
              'tools\\perf\\run_benchmark']:
       v = 'src/tools/perf/run_benchmark'
     command_to_run.append(v)
   test_cfg.update({'command': ' '.join(command_to_run)})