Fix missing HEADLESS_EXPORT defines

headless/public/util/flat_dom_tree_extractor.h

 // Copyright 2017 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_DOM_TREE_EXTRACTOR_H_
 #define HEADLESS_PUBLIC_UTIL_DOM_TREE_EXTRACTOR_H_
 
 #include <unordered_map>
 #include <vector>
 
 #include "base/macros.h"
 #include "headless/public/devtools/domains/css.h"
 #include "headless/public/devtools/domains/dom.h"
+#include "headless/public/headless_export.h"
 
 namespace headless {
 class HeadlessDevToolsClient;
 
 // A utility class for extracting information from the DOM via DevTools. In
 // addition, it also extracts details of bounding boxes and layout text (NB the
 // exact layout should not be regarded as stable, it's subject to change without
 // notice).
-class FlatDomTreeExtractor {
+class HEADLESS_EXPORT FlatDomTreeExtractor {
  public:
   explicit FlatDomTreeExtractor(HeadlessDevToolsClient* devtools_client);
   ~FlatDomTreeExtractor();
 
   using NodeId = int;
   using Index = size_t;
 
-  class DomTree {
+  class HEADLESS_EXPORT DomTree {
    public:
     DomTree();
     DomTree(DomTree&& other);
     ~DomTree();
 
     // Flattened dom tree. The root node is always the first entry.
     std::vector<const dom::Node*> dom_nodes_;
 
     // Map of node IDs to indexes into |dom_nodes_|.
     std::unordered_map<NodeId, Index> node_id_to_index_;
@@ skipping 39 matching lines @@
   bool work_in_progress_;
   HeadlessDevToolsClient* devtools_client_;  // NOT OWNED
   base::WeakPtrFactory<FlatDomTreeExtractor> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(FlatDomTreeExtractor);
 };
 
 }  // namespace headless
 
 #endif  // HEADLESS_PUBLIC_UTIL_DOM_TREE_EXTRACTOR_H_