Fix a QUIC bug in which PING frames were not being ACK'd.

net/quic/quic_connection.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 //
 // The entity that handles framing writes for a Quic client or server.
 // Each QuicSession will have a connection associated with it.
 //
 // On the server side, the Dispatcher handles the raw reads, and hands off
 // packets via ProcessUdpPacket for framing and processing.
 //
@@ skipping 675 matching lines @@
   EncryptionLevel last_decrypted_packet_level_;
   QuicPacketHeader last_header_;
   std::vector<QuicStreamFrame> last_stream_frames_;
   std::vector<QuicAckFrame> last_ack_frames_;
   std::vector<QuicCongestionFeedbackFrame> last_congestion_frames_;
   std::vector<QuicStopWaitingFrame> last_stop_waiting_frames_;
   std::vector<QuicRstStreamFrame> last_rst_frames_;
   std::vector<QuicGoAwayFrame> last_goaway_frames_;
   std::vector<QuicWindowUpdateFrame> last_window_update_frames_;
   std::vector<QuicBlockedFrame> last_blocked_frames_;
+  std::vector<QuicPingFrame> last_ping_frames_;
   std::vector<QuicConnectionCloseFrame> last_close_frames_;
 
   QuicCongestionFeedbackFrame outgoing_congestion_feedback_;
 
   // Track some peer state so we can do less bookkeeping
   // Largest sequence sent by the peer which had an ack frame (latest ack info).
   QuicPacketSequenceNumber largest_seen_packet_with_ack_;
 
   // Largest sequence number sent by the peer which had a stop waiting frame.
   QuicPacketSequenceNumber largest_seen_packet_with_stop_waiting_;
@@ skipping 100 matching lines @@
   // If non-empty this contains the set of versions received in a
   // version negotiation packet.
   QuicVersionVector server_supported_versions_;
 
   DISALLOW_COPY_AND_ASSIGN(QuicConnection);
 };
 
 }  // namespace net
 
 #endif  // NET_QUIC_QUIC_CONNECTION_H_