Move QuicIoVector into its own header file. No behavior change.

net/quic/core/quic_packet_creator.h

 // Copyright (c) 2012 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.
 //
 // Accumulates frames for the next packet until more frames no longer fit or
 // it's time to create a packet from them. If multipath enabled, only creates
 // packets on one path at the same time. Currently, next packet number is
 // tracked per-path.
 
 #ifndef NET_QUIC_QUIC_PACKET_CREATOR_H_
 #define NET_QUIC_QUIC_PACKET_CREATOR_H_
 
 #include <stddef.h>
 
 #include <memory>
 #include <string>
 #include <unordered_map>
 #include <utility>
 #include <vector>
 
 #include "base/macros.h"
 #include "base/strings/string_piece.h"
 #include "net/base/net_export.h"
 #include "net/quic/core/quic_framer.h"
+#include "net/quic/core/quic_iovector.h"
 #include "net/quic/core/quic_protocol.h"
 
 namespace net {
 namespace test {
 class QuicPacketCreatorPeer;
 }
 
 class NET_EXPORT_PRIVATE QuicPacketCreator {
  public:
   // A delegate interface for further processing serialized packet.
@@ skipping 273 matching lines @@
 
   // Map mapping path_id to last sent packet number on the path.
   std::unordered_map<QuicPathId, QuicPacketNumber> multipath_packet_number_;
 
   DISALLOW_COPY_AND_ASSIGN(QuicPacketCreator);
 };
 
 }  // namespace net
 
 #endif  // NET_QUIC_QUIC_PACKET_CREATOR_H_