RenderProxyBoxWithHitTestBehavior({HitTestBehavior behavior: HitTestBehavior.deferToChild, RenderBox child })

Initializes member variables for subclasses.

By default, the behavior is HitTestBehavior.deferToChild.

Source 

RenderProxyBoxWithHitTestBehavior({
  this.behavior: HitTestBehavior.deferToChild,
  RenderBox child
}) : super(child);