message: Minimize calls to tesor_util.constant_value in array_grad._StridedSliceGrad.
diff: @@ -273,14 +273,14 @@ def _StridedSliceGrad(op, grad):
  # be the same.
  x = array_ops.shape(op.inputs[0], out_type=begin.dtype)
  - if tensor_util.constant_value(x) is not None:
  - x = tensor_util.constant_value(x)
  - if tensor_util.constant_value(begin) is not None:
  - begin = tensor_util.constant_value(begin)
  - if tensor_util.constant_value(end) is not None:
  - end = tensor_util.constant_value(end)
  - if tensor_util.constant_value(strides) is not None:
  - strides = tensor_util.constant_value(strides)
  + x_static = tensor_util.constant_value(x)
  + x = x_static if x_static is not None else x
  + begin_static = tensor_util.constant_value(begin)
  + begin = begin_static if begin_static is not None else begin
  + end_static = tensor_util.constant_value(end)
  + end = end_static if end_static is not None else end
  + strides_static = tensor_util.constant_value(strides)
  + strides = strides_static if strides_static is not None else strides
  return array_ops.strided_slice_grad(
  x,
  