Update from https://crrev.com/311346

net/quic/quic_packet_generator.h

Index: net/quic/quic_packet_generator.h
diff --git a/net/quic/quic_packet_generator.h b/net/quic/quic_packet_generator.h
index f35f9bd52a07490fc6de6f8f12358494c01f7e3d..24dc97c4772264efa74f4423ea74902807fa9cbd 100644
--- a/net/quic/quic_packet_generator.h
+++ b/net/quic/quic_packet_generator.h
@@ -53,6 +53,7 @@
 #ifndef NET_QUIC_QUIC_PACKET_GENERATOR_H_
 #define NET_QUIC_QUIC_PACKET_GENERATOR_H_
 
+#include "base/containers/hash_tables.h"
 #include "net/quic/quic_ack_notifier.h"
 #include "net/quic/quic_packet_creator.h"
 #include "net/quic/quic_sent_packet_manager.h"
@@ -247,6 +248,9 @@ class NET_EXPORT_PRIVATE QuicPacketGenerator {
   scoped_ptr<QuicCongestionFeedbackFrame> pending_feedback_frame_;
   scoped_ptr<QuicStopWaitingFrame> pending_stop_waiting_frame_;
 
+  // Stores notifiers that should be attached to the next serialized packet.
+  base::hash_set<QuicAckNotifier*> ack_notifiers_;
+
   DISALLOW_COPY_AND_ASSIGN(QuicPacketGenerator);
 };