Fix missing HEADLESS_EXPORT defines

headless/lib/browser/headless_browser_impl.h

 // Copyright 2015 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_LIB_BROWSER_HEADLESS_BROWSER_IMPL_H_
 #define HEADLESS_LIB_BROWSER_HEADLESS_BROWSER_IMPL_H_
 
 #include "headless/public/headless_browser.h"
 
 #include <memory>
 #include <string>
 #include <unordered_map>
 #include <vector>
 
 #include "base/memory/weak_ptr.h"
 #include "content/public/browser/web_contents.h"
 #include "headless/lib/browser/headless_devtools_manager_delegate.h"
 #include "headless/lib/browser/headless_web_contents_impl.h"
+#include "headless/public/headless_export.h"
 
 #if defined(USE_AURA)
 #include "headless/lib/browser/headless_window_tree_host.h"
 
 namespace aura {
 namespace client {
 class FocusClient;
 }
 }
 #endif
 
 namespace headless {
 
 class HeadlessBrowserContextImpl;
 class HeadlessBrowserMainParts;
 
-class HeadlessBrowserImpl : public HeadlessBrowser {
+// Exported for tests.
+class HEADLESS_EXPORT HeadlessBrowserImpl : public HeadlessBrowser {
  public:
   HeadlessBrowserImpl(
       const base::Callback<void(HeadlessBrowser*)>& on_start_callback,
       HeadlessBrowser::Options options);
   ~HeadlessBrowserImpl() override;
 
   // HeadlessBrowser implementation:
   HeadlessBrowserContext::Builder CreateBrowserContextBuilder() override;
   scoped_refptr<base::SingleThreadTaskRunner> BrowserFileThread()
       const override;
@@ skipping 54 matching lines @@
 
   base::WeakPtrFactory<HeadlessBrowserImpl> weak_ptr_factory_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(HeadlessBrowserImpl);
 };
 
 }  // namespace headless
 
 #endif  // HEADLESS_LIB_BROWSER_HEADLESS_BROWSER_IMPL_H_