message: Save a couple copy of dynamics in QLog
  Summary: Two of them can be moved. Two of them can be saved with copy-elision.
diff: @@ -179,8 +179,8 @@ folly::dynamic ReadAckFrameLog::toDynamic() const {
  folly::dynamic ackRangeDynamic = folly::dynamic::array();
  for (const auto& b : ackBlocks) {
  - folly::dynamic subArray = folly::dynamic::array(b.startPacket, b.endPacket);
  - ackRangeDynamic.push_back(subArray);
  + ackRangeDynamic.push_back(
  + folly::dynamic::array(b.startPacket, b.endPacket));
  }
  d["acked_ranges"] = ackRangeDynamic;
  d["frame_type"] = toString(FrameType::ACK);
  @@ -193,8 +193,7 @@ folly::dynamic WriteAckFrameLog::toDynamic() const {
  folly::dynamic ackRangeDynamic = folly::dynamic::array();
  for (auto it = ackBlocks.cbegin(); it != ackBlocks.cend(); ++it) {
  - folly::dynamic subArray = folly::dynamic::array(it->start, it->end);
  - ackRangeDynamic.push_back(subArray);
  + ackRangeDynamic.push_back(folly::dynamic::array(it->start, it->end));
  }
  d["acked_ranges"] = ackRangeDynamic;
  d["frame_type"] = toString(FrameType::ACK);
  @@ -232,7 +231,7 @@ folly::dynamic QLogPacketEvent::toDynamic() const {
  "packet_number", packetNum);
  data["packet_type"] = packetType;
  - d.push_back(data);
  + d.push_back(std::move(data));
  return d;
  }
  @@ -245,7 +244,7 @@ folly::dynamic QLogVersionNegotiationEvent::toDynamic() const {
  data["header"] = folly::dynamic::object("packet_size", packetSize);
  data["packet_type"] = packetType;
  - d.push_back(data);
  + d.push_back(std::move(data));
  return d;
  }
  