connection.go: batched OnAck calls

connection.go

@@ -187,17 +187,22 @@ func (c *connection) receive(sequenceID uint32, frames []frame.Frame) (err error
 func (c *connection) handle(fr frame.Frame) (err error) {
 	switch fr := fr.(type) {
 	case *frame.Acknowledgement:
+		var ackBytes float64
 		for i, r := range fr.Ranges {
 			for j := r[0]; j <= r[1]; j++ {
 				if entry := c.retransmission.remove(j); entry != nil {
-					c.cc.OnAck(float64(len(entry.payload)))
+					ackBytes += float64(len(entry.payload))
 					if i == len(fr.Ranges)-1 && j == r[1] {
 						c.rtt.Add(time.Duration(time.Since(entry.timestamp).Nanoseconds()-fr.Delay) * time.Nanosecond)
 					}
 				}
 			}
 		}
 
+		if ackBytes > 0 {
+			c.cc.OnAck(ackBytes)
+		}
+
 		if fr.Type == frame.AcknowledgementWithGaps {
 			for _, sequenceID := range frame.GenerateAcknowledgementGaps(fr.Ranges) {
 				c.retransmission.nack(sequenceID)