message: Adding an XLA kernel registration for kDeviceRetOp that returns int32 tensors
  in device memory rather than host memory.
diff: @@ -210,6 +210,8 @@ class XlaAssignVariableOp : public AsyncOpKernel {
  .TypeConstraint<ResourceHandle>("T") \
  .HostMemory("input"), \
  RetvalOp); \
  + REGISTER_KERNEL_BUILDER( \
  + Name(kDeviceRetOp).Device(DEVICE).TypeConstraint<int32>("T"), RetvalOp); \
  \
  REGISTER_KERNEL_BUILDER( \
  Name("RemoteCall").Device(DEVICE).HostMemory("target"), RemoteCallOp); \
  