Is "need_backprop" used in the "GradientSilent" layer?

[Hub-Tian]

@yuhuayc I think the input "need_backprop" is used to decide whether the gradient should be propagate backward or not. However, I can not find any reference in the defination of the "GradientSilent" layer in'\caffe-fast-rcnn\src\caffe\layers\gradient_silent_layer.cpp'. I wonder if I misunderstand the usage of the input "need_backprop".

layer {
name: "loss_cls_filter"
type: "GradientSilent"
bottom: "cls_score"
bottom: "need_backprop"
top: "cls_score_filter"
}