Fix missing HEADLESS_EXPORT defines

headless/public/util/deterministic_http_protocol_handler.h

Index: headless/public/util/deterministic_http_protocol_handler.h
diff --git a/headless/public/util/deterministic_http_protocol_handler.h b/headless/public/util/deterministic_http_protocol_handler.h
index 89d76cbc692304b3f325c02e56ce0fcb11529cb3..05d5215402a8ffbeef445c2307f3d5f8354cfee8 100644
--- a/headless/public/util/deterministic_http_protocol_handler.h
+++ b/headless/public/util/deterministic_http_protocol_handler.h
@@ -8,6 +8,7 @@
 #include <memory>
 
 #include "base/single_thread_task_runner.h"
+#include "headless/public/headless_export.h"
 #include "net/url_request/url_request_job_factory.h"
 
 namespace net {
@@ -22,7 +23,7 @@ class DeterministicDispatcher;
 // will return in order of creation, regardless of what order the network
 // returns them in.  This helps remove one large source of network related
 // non determinism at the cost of slower page loads.
-class DeterministicHttpProtocolHandler
+class HEADLESS_EXPORT DeterministicHttpProtocolHandler
     : public net::URLRequestJobFactory::ProtocolHandler {
  public:
   // Note |deterministic_dispatcher| is expected to be shared across a number of