Fix net_export.h includes.

net/disk_cache/blockfile/backend_impl.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.
 
 // See net/disk_cache/disk_cache.h for the public interface of the cache.
 
 #ifndef NET_DISK_CACHE_BLOCKFILE_BACKEND_IMPL_H_
 #define NET_DISK_CACHE_BLOCKFILE_BACKEND_IMPL_H_
 
 #include <stdint.h>
 
 #include <unordered_map>
 
 #include "base/files/file_path.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/timer/timer.h"
+#include "net/base/net_export.h"
 #include "net/disk_cache/blockfile/block_files.h"
 #include "net/disk_cache/blockfile/eviction.h"
 #include "net/disk_cache/blockfile/in_flight_backend_io.h"
 #include "net/disk_cache/blockfile/rankings.h"
 #include "net/disk_cache/blockfile/stats.h"
 #include "net/disk_cache/blockfile/stress_support.h"
 #include "net/disk_cache/blockfile/trace.h"
 #include "net/disk_cache/disk_cache.h"
 
 namespace base {
@@ skipping 380 matching lines @@
   base::WaitableEvent done_;  // Signals the end of background work.
   scoped_refptr<TraceObject> trace_object_;  // Initializes internal tracing.
   base::WeakPtrFactory<BackendImpl> ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(BackendImpl);
 };
 
 }  // namespace disk_cache
 
 #endif  // NET_DISK_CACHE_BLOCKFILE_BACKEND_IMPL_H_