Added support for header and footer inside other sections, according to HTML API Mappings 1.0.

ui/accessibility/ax_position.h

Index: ui/accessibility/ax_position.h
diff --git a/ui/accessibility/ax_position.h b/ui/accessibility/ax_position.h
new file mode 100644
index 0000000000000000000000000000000000000000..293b23e36f11d70f0880e025819327714885ce4f
--- /dev/null
+++ b/ui/accessibility/ax_position.h
@@ -0,0 +1,35 @@
+// Copyright 2016 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_POSITION_H_

[dmazzoni, 2016/08/10 20:45:52]

Looks cool but doesn't belong in this change?

+#define UI_ACCESSIBILITY_AX_POSITION_H_
+
+#include "ui/accessibility/ax_node.h"
+
+namespace ui {
+
+// A position in the |AXTree|.
+class AX_EXPORT AXPosition {
+ public:
+  AXPosition();
+  AXPosition(AXNode* anchor, int offset);
+  virtual ~AXPosition();
+
+  static AXPosition* CreateNullPosition();
+
+  AXNode* get_anchor() const { return anchor_; }
+  int get_offset() const { return offset_; }
+
+  bool IsNull() const;
+  AXPosition ToLeafEquivalent() const;
+  AXPosition GetCorrespondingPositionInParent(const AXNode& parent) const;
+
+ private:
+  AXNode* anchor_;
+  int offset_;
+};
+
+}  // namespace ui
+
+#endif  // UI_ACCESSIBILITY_AX_POSITION_H_