message: Add CancellationManager to LoopCondOp
diff: @@ -600,6 +600,15 @@ LoopCondOp::LoopCondOp(OpKernelConstruction* context) : OpKernel(context) {}
  LoopCondOp::~LoopCondOp() = default;
  void LoopCondOp::Compute(OpKernelContext* context) {
  + CancellationManager* cm = context->cancellation_manager();
  + bool already_cancelled = cm->IsCancelled();
  +
  + if (already_cancelled) {
  + Tensor continue_running(false);
  + context->set_output(0, continue_running);
  + return;
  + }
  +
  context->set_output(0, context->input(0));
  }
  