message: [TF2XLA] Use a better definition of SoftplusGrad.
diff: @@ -220,9 +220,7 @@ XLA_MAKE_BINARY(SigmoidGrad,
  xla::Mul(xla::Mul(rhs, lhs),
  xla::Sub(XlaHelpers::One(b, input_type(0)), lhs)));
  -XLA_MAKE_BINARY(SoftplusGrad,
  - xla::Div(lhs, xla::Add(xla::Exp(xla::Neg(rhs)),
  - XlaHelpers::One(b, input_type(1)))));
  +XLA_MAKE_BINARY(SoftplusGrad, xla::Mul(lhs, xla::Logistic(rhs)));
  // softsigngrad(gradients, features) = gradients / (1 + abs(features)) ** 2
  XLA_MAKE_BINARY(SoftsignGrad,
  