In QUIC, send data is copied to streams rather than frames. Protected by FLAGS_quic_reloadable_flag…

net/quic/core/quic_stream_frame_data_producer.h

Index: net/quic/core/quic_stream_frame_data_producer.h
diff --git a/net/quic/core/quic_stream_frame_data_producer.h b/net/quic/core/quic_stream_frame_data_producer.h
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+// Copyright (c) 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef NET_QUIC_CORE_QUIC_STREAM_FRAME_DATA_PRODUCER_H_
+#define NET_QUIC_CORE_QUIC_STREAM_FRAME_DATA_PRODUCER_H_
+
+#include "net/quic/core/quic_iovector.h"
+#include "net/quic/core/quic_types.h"
+
+namespace net {
+
+class QuicDataWriter;
+
+// Pure virtual class to save and retrieve stream data.
+class QUIC_EXPORT_PRIVATE QuicStreamFrameDataProducer {
+ public:
+  virtual ~QuicStreamFrameDataProducer() {}
+
+  // Save |data_length| data starts at |iov_offset| in |iov|.
+  virtual void SaveStreamData(QuicStreamId id,
+                              QuicIOVector iov,
+                              size_t iov_offset,
+                              QuicStreamOffset offset,
+                              QuicByteCount data_length) = 0;
+
+  // Let |writer| write |data_length| data with |offset| of stream |id|. Returns
+  // false when the writing fails either because stream is closed or
+  // corresponding data is failed to be retrieved. This method allows writing a
+  // single stream frame from data that spans multiple buffers.
+  virtual bool WriteStreamData(QuicStreamId id,
+                               QuicStreamOffset offset,
+                               QuicByteCount data_length,
+                               QuicDataWriter* writer) = 0;
+};
+
+}  // namespace net
+
+#endif  // NET_QUIC_CORE_QUIC_STREAM_FRAME_DATA_PRODUCER_H_