Cache the value of GetMaxPlaintextSize in QuicPacketCreator. No functional change.

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 1fc363e5c5e69432a153aa49dc59781bccfd6e86..fd176268512c9d96ff17577b3d6cfdc2349ca663 100644
--- a/net/quic/quic_packet_generator.h
+++ b/net/quic/quic_packet_generator.h
@@ -178,6 +178,9 @@ class NET_EXPORT_PRIVATE QuicPacketGenerator {
   // fires.
   QuicTime::Delta GetFecTimeout(QuicPacketSequenceNumber sequence_number);
 
+  // Sets the encrypter to use for the encryption level.
+  void SetEncrypter(EncryptionLevel level, QuicEncrypter* encrypter);
+
   // Sets the encryption level that will be applied to new packets.
   void set_encryption_level(EncryptionLevel level);