message: Disable caching_device for mirrored variables.
diff: @@ -109,6 +109,9 @@ class MirroredStrategy(distribute_lib.DistributionStrategy):
  if tower_local is not None:
  kwargs["trainable"] = False
  + # Ignore user-specified caching device, not needed for mirrored variables.
  + kwargs.pop("caching_device", None)
  +
  # TODO(josh11b,apassos): It would be better if variable initialization
  # was never recorded on the tape instead of having to do this manually
  # here.
  