[Android] Adds directory cleanup/creation for code coverage

build/android/buildbot/bb_device_steps.py

Index: build/android/buildbot/bb_device_steps.py
diff --git a/build/android/buildbot/bb_device_steps.py b/build/android/buildbot/bb_device_steps.py
index 5acc976923c05414d67ec8a6a525ea9e62574f8e..e72ba1ef4a8ab1fca844e6b3fe559a2846b48831 100755
--- a/build/android/buildbot/bb_device_steps.py
+++ b/build/android/buildbot/bb_device_steps.py
@@ -281,7 +281,7 @@ def DeviceStatusCheck(_):
 def GetDeviceSetupStepCmds():
   return [
     ('provision_devices', ProvisionDevices),
-    ('device_status_check', DeviceStatusCheck)
+    ('device_status_check', DeviceStatusCheck),
   ]
 
 
@@ -385,6 +385,9 @@ def MainTestWrapper(options):
       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)