Refactor StringPiece hash.

ui/accessibility/ax_tree_update.h

 // Copyright 2013 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 UI_ACCESSIBILITY_AX_TREE_UPDATE_H_
 #define UI_ACCESSIBILITY_AX_TREE_UPDATE_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <string>
 #include <vector>
 
+#include "base/containers/hash_tables.h"
 #include "base/strings/string_number_conversions.h"
 #include "ui/accessibility/ax_node_data.h"
 #include "ui/accessibility/ax_tree_data.h"
 
 namespace ui {
 
 // An AXTreeUpdate is a serialized representation of an atomic change
 // to an AXTree. The sender and receiver must be in sync; the update
 // is only meant to bring the tree from a specific previous state into
 // its next state. Trying to apply it to the wrong tree should immediately
@@ skipping 82 matching lines @@
     for (size_t j = 0; j < nodes[i].child_ids.size(); ++j)
       id_to_indentation[nodes[i].child_ids[j]] = indent + 1;
   }
 
   return result;
 }
 
 }  // namespace ui
 
 #endif  // UI_ACCESSIBILITY_AX_TREE_UPDATE_H_