[Android] Adds directory cleanup/creation for code coverage

build/android/buildbot/bb_device_steps.py

 #!/usr/bin/env python
 # Copyright (c) 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.
 
 import collections
 import glob
 import hashlib
 import multiprocessing
 import os
@@ skipping 263 matching lines @@
 
 def DeviceStatusCheck(_):
   bb_annotations.PrintNamedStep('device_status_check')
   RunCmd(['build/android/buildbot/bb_device_status_check.py'],
          halt_on_failure=True)
 
 
 def GetDeviceSetupStepCmds():
   return [
     ('provision_devices', ProvisionDevices),
-    ('device_status_check', DeviceStatusCheck)
+    ('device_status_check', DeviceStatusCheck),
   ]
 
 
 def RunUnitTests(options):
   RunTestSuites(options, gtest_config.STABLE_TEST_SUITES)
 
 
 def RunInstrumentationTests(options):
   for test in INSTRUMENTATION_TESTS.itervalues():
     RunInstrumentationSuite(options, test)
@@ skipping 83 matching lines @@
     SpawnLogcatMonitor()
 
     # Run all device setup steps
     for _, cmd in GetDeviceSetupStepCmds():
       cmd(options)
 
     if options.install:
       test_obj = INSTRUMENTATION_TESTS[options.install]
       InstallApk(options, test_obj, print_step=True)
 
+    if options.coverage_bucket:
+      RunCmd(['rm', '-rf', options.coverage_dir])
+
     if options.test_filter:
       bb_utils.RunSteps(options.test_filter, GetTestStepCmds(), options)
 
     if options.coverage_bucket:
       GenerateJavaCoverageReport(options)
 
     if options.experimental:
       RunTestSuites(options, gtest_config.EXPERIMENTAL_TEST_SUITES)
 
   finally:
@@ skipping 49 matching lines @@
   setattr(options, 'target', options.factory_properties.get('target', 'Debug'))
   if options.coverage_bucket:
     setattr(options, 'coverage_dir',
             os.path.join(CHROME_SRC, 'out', options.target, 'coverage'))
 
   MainTestWrapper(options)
 
 
 if __name__ == '__main__':
   sys.exit(main(sys.argv))