Fix missing HEADLESS_EXPORT defines

headless/public/util/generic_url_request_job.h

Index: headless/public/util/generic_url_request_job.h
diff --git a/headless/public/util/generic_url_request_job.h b/headless/public/util/generic_url_request_job.h
index 751f497c66ab7c8a014ba2c9d4b89be150c93578..47d853c51daed3544a4f8e14171ec6afc8481d2c 100644
--- a/headless/public/util/generic_url_request_job.h
+++ b/headless/public/util/generic_url_request_job.h
@@ -13,6 +13,7 @@
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/weak_ptr.h"
+#include "headless/public/headless_export.h"
 #include "headless/public/util/managed_dispatch_url_request_job.h"
 #include "headless/public/util/url_fetcher.h"
 #include "net/base/net_errors.h"
@@ -34,8 +35,9 @@ class URLRequestDispatcher;
 // 1. The delegate can extension observe / cancel and redirect requests
 // 2. The delegate can optionally provide the results, otherwise the specifed
 //    fetcher is invoked.
-class GenericURLRequestJob : public ManagedDispatchURLRequestJob,
-                             public URLFetcher::ResultListener {
+class HEADLESS_EXPORT GenericURLRequestJob
+    : public ManagedDispatchURLRequestJob,
+      public URLFetcher::ResultListener {
  public:
   enum class RewriteResult { kAllow, kDeny, kFailure };
   using RewriteCallback = std::function<