external-release-note: Adding a flag for enforcement of the single-packet-CHLO policy.

net/quic/core/quic_packet_creator.cc

Index: net/quic/core/quic_packet_creator.cc
diff --git a/net/quic/core/quic_packet_creator.cc b/net/quic/core/quic_packet_creator.cc
index 2b2a8c141d71a6a0cc6f03343d326b7aac8d347f..d84b084a5e3eec734ad383c00c411b116e8f2e6f 100644
--- a/net/quic/core/quic_packet_creator.cc
+++ b/net/quic/core/quic_packet_creator.cc
@@ -138,7 +138,8 @@ bool QuicPacketCreator::ConsumeData(QuicStreamId id,
       strncmp(frame->stream_frame->data_buffer,
               reinterpret_cast<const char*>(&kCHLO), sizeof(kCHLO)) == 0) {
     DCHECK_EQ(static_cast<size_t>(0), iov_offset);
-    if (frame->stream_frame->data_length < iov.iov->iov_len) {
+    if (FLAGS_quic_enforce_single_packet_chlo &&
+        frame->stream_frame->data_length < iov.iov->iov_len) {
       const string error_details = "Client hello won't fit in a single packet.";
       QUIC_BUG << error_details << " Constructed stream frame length: "
                << frame->stream_frame->data_length