relnote: Allow individual QUIC writers to limit the maximum packet size.

net/quic/quic_packet_writer.h

Index: net/quic/quic_packet_writer.h
diff --git a/net/quic/quic_packet_writer.h b/net/quic/quic_packet_writer.h
index b8ee2933bd2178c191871280cfe2c7489c4672b6..b1eb148a52097f31a5dcdba4b6f4c5c6ce2e753c 100644
--- a/net/quic/quic_packet_writer.h
+++ b/net/quic/quic_packet_writer.h
@@ -6,6 +6,7 @@
 #define NET_QUIC_QUIC_PACKET_WRITER_H_
 
 #include "net/base/ip_endpoint.h"
+#include "net/quic/quic_protocol.h"
 
 namespace net {
 
@@ -38,6 +39,12 @@ class NET_EXPORT_PRIVATE QuicPacketWriter {
   // Records that the socket has become writable, for example when an EPOLLOUT
   // is received or an asynchronous write completes.
   virtual void SetWritable() = 0;
+
+  // Returns the maximum size of the packet which can be written using this
+  // writer for the supplied peer address.  This size may actually exceed the
+  // size of a valid QUIC packet.
+  virtual QuicByteCount GetMaxPacketSize(
+      const IPEndPoint& peer_address) const = 0;
 };
 
 }  // namespace net