code: func (p *peerConnection) SetHeadersIdle(delivered int) {
  	p.setIdle(p.headerStarted, delivered, &p.headerThroughput, &p.headerIdle)
  }
docs: // SetHeadersIdle sets the peer to idle, allowing it to execute new header retrieval
  // requests. Its estimated header retrieval throughput is updated with that measured
  // just now.