[Android] Don't use a device blacklist if one isn't provided.

build/android/test_runner.py

Index: build/android/test_runner.py
diff --git a/build/android/test_runner.py b/build/android/test_runner.py
index 204c81c0e6bbacd811d5d0af370fac233fbc2745..18b87adec8993a4f364f7972908b2426291ac81b 100755
--- a/build/android/test_runner.py
+++ b/build/android/test_runner.py
@@ -895,13 +895,10 @@ def _GetAttachedDevices(blacklist_file, test_device):
   Returns:
     A list of attached devices.
   """
-  if not blacklist_file:
-    # TODO(jbudorick): Remove this once bots pass the blacklist file.
-    blacklist_file = device_blacklist.BLACKLIST_JSON
-    logging.warning('Using default device blacklist %s',
-                    device_blacklist.BLACKLIST_JSON)
+  blacklist = (device_blacklist.Blacklist(blacklist_file)
+               if blacklist_file
+               else None)
 
-  blacklist = device_blacklist.Blacklist(blacklist_file)
   attached_devices = device_utils.DeviceUtils.HealthyDevices(blacklist)
   if test_device:
     test_device = [d for d in attached_devices if d == test_device]