[forbots] IWYU for ax_enums.h

ui/accessibility/tree_generator.cc

 // Copyright 2014 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.
 
 #include "ui/accessibility/tree_generator.h"
 
+#include "ui/accessibility/ax_enums.h"
 #include "ui/accessibility/ax_serializable_tree.h"
 #include "ui/accessibility/ax_tree.h"
 
 namespace ui {
 
 static int UniqueTreeCountForNodeCount(int node_count,
                                        bool permutations) {
   int unique_tree_count = 1;
 
   // (n-1)! for the possible trees.
@@ skipping 86 matching lines @@
     int parent_index = (tree_index % i);
     tree_index /= i;
     update.nodes[parent_index].child_ids.push_back(permuted[i]);
   }
 
   // Unserialize the tree update into the destination tree.
   CHECK(out_tree->Unserialize(update)) << out_tree->error();
 };
 
 }  // namespace ui