message: Pack holes in quic::AckState
  Summary: As in title.
diff: @@ -18,19 +18,10 @@ namespace quic {
  // Ack and PacketNumber states. This is per-packet number space.
  struct AckState {
  - AckBlocks acks;
  // Largest ack that has been written to a packet
  folly::Optional<PacketNum> largestAckScheduled;
  - // Flag indicating that if we need to send ack immediately. This will be set
  - // to true if we got packets with retransmittable data and haven't sent the
  - // ack for the first time.
  - // TODO: upgrade this to be bundled like non-retransmittable packets once we
  - // figured out how to do timeout.
  - bool needsToSendAckImmediately{false};
  // Count of outstanding packets received with only non-retransmittable data.
  uint64_t numNonRxPacketsRecvd{0};
  - // Count of oustanding packets received with retransmittable data.
  - uint8_t numRxPacketsRecvd{0};
  // The receive time of the largest ack packet
  folly::Optional<TimePoint> largestRecvdPacketTime;
  // Latest packet number acked by peer
  @@ -41,6 +32,15 @@ struct AckState {
  folly::Optional<PacketNum> largestReceivedAtLastCloseSent;
  // Next PacketNum we will send for packet in this packet number space
  PacketNum nextPacketNum{0};
  + AckBlocks acks;
  + // Flag indicating that if we need to send ack immediately. This will be set
  + // to true if we got packets with retransmittable data and haven't sent the
  + // ack for the first time.
  + // TODO: upgrade this to be bundled like non-retransmittable packets once we
  + // figured out how to do timeout.
  + bool needsToSendAckImmediately{false};
  + // Count of oustanding packets received with retransmittable data.
  + uint8_t numRxPacketsRecvd{0};
  };
  struct AckStates {
  