Fix net_export.h includes.

net/quic/core/quic_simple_buffer_allocator.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.
 
 #ifndef NET_QUIC_SIMPLE_BUFFER_ALLOCATOR_H_
 #define NET_QUIC_SIMPLE_BUFFER_ALLOCATOR_H_
 
+#include "net/base/net_export.h"
 #include "net/quic/core/quic_protocol.h"
 
 namespace net {
 
 class NET_EXPORT_PRIVATE SimpleBufferAllocator : public QuicBufferAllocator {
  public:
   char* New(size_t size) override;
   char* New(size_t size, bool flag_enable) override;
   void Delete(char* buffer) override;
 };
 
 }  // namespace net
 
 #endif  // NET_QUIC_SIMPLE_BUFFER_ALLOCATOR_H_