Stop returning unused return value from QuicPacketCreator::CopyToBuffer. No functional change.

net/quic/test_tools/quic_packet_creator_peer.h

Index: net/quic/test_tools/quic_packet_creator_peer.h
diff --git a/net/quic/test_tools/quic_packet_creator_peer.h b/net/quic/test_tools/quic_packet_creator_peer.h
index 6849c1f1bd1ea9ad2ff1b87a5a40f38821d43291..7c56c456f396290ef8abb0363c5ad6657a4508bb 100644
--- a/net/quic/test_tools/quic_packet_creator_peer.h
+++ b/net/quic/test_tools/quic_packet_creator_peer.h
@@ -37,13 +37,13 @@ class QuicPacketCreatorPeer {
   static void SetPacketNumber(QuicPacketCreator* creator, QuicPacketNumber s);
   static void FillPacketHeader(QuicPacketCreator* creator,
                                QuicPacketHeader* header);
-  static size_t CreateStreamFrame(QuicPacketCreator* creator,
-                                  QuicStreamId id,
-                                  QuicIOVector iov,
-                                  size_t iov_offset,
-                                  QuicStreamOffset offset,
-                                  bool fin,
-                                  QuicFrame* frame);
+  static void CreateStreamFrame(QuicPacketCreator* creator,
+                                QuicStreamId id,
+                                QuicIOVector iov,
+                                size_t iov_offset,
+                                QuicStreamOffset offset,
+                                bool fin,
+                                QuicFrame* frame);
   static SerializedPacket SerializeAllFrames(QuicPacketCreator* creator,
                                              const QuicFrames& frames,
                                              char* buffer,