Fix missing HEADLESS_EXPORT defines

headless/public/util/expedited_dispatcher.h

 // Copyright 2016 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 HEADLESS_PUBLIC_UTIL_EXPEDITED_DISPATCHER_H_
 #define HEADLESS_PUBLIC_UTIL_EXPEDITED_DISPATCHER_H_
 
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/single_thread_task_runner.h"
+#include "headless/public/headless_export.h"
 #include "headless/public/util/url_request_dispatcher.h"
 #include "net/base/net_errors.h"
 
 namespace headless {
 
 class ManagedDispatchURLRequestJob;
 
 // This class dispatches calls to OnHeadersComplete and OnStartError
 // immediately sacrificing determinism for performance.
-class ExpeditedDispatcher : public URLRequestDispatcher {
+class HEADLESS_EXPORT ExpeditedDispatcher : public URLRequestDispatcher {
  public:
   explicit ExpeditedDispatcher(
       scoped_refptr<base::SingleThreadTaskRunner> io_thread_task_runner);
   ~ExpeditedDispatcher() override;
 
   // UrlRequestDispatcher implementation:
   void JobCreated(ManagedDispatchURLRequestJob* job) override;
   void JobKilled(ManagedDispatchURLRequestJob* job) override;
   void JobFailed(ManagedDispatchURLRequestJob* job, net::Error error) override;
   void DataReady(ManagedDispatchURLRequestJob* job) override;
   void JobDeleted(ManagedDispatchURLRequestJob* job) override;
   void NavigationRequested(
       std::unique_ptr<NavigationRequest> navigation_request) override;
 
  private:
   scoped_refptr<base::SingleThreadTaskRunner> io_thread_task_runner_;
 
   DISALLOW_COPY_AND_ASSIGN(ExpeditedDispatcher);
 };
 
 }  // namespace headless
 
 #endif  // HEADLESS_PUBLIC_UTIL_EXPEDITED_DISPATCHER_H_