Creates AXPosition to uniquely identify a position in the accessibility tree

ui/accessibility/ax_range.h

Index: ui/accessibility/ax_range.h
diff --git a/ui/accessibility/ax_range.h b/ui/accessibility/ax_range.h
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index 0000000000000000000000000000000000000000..28f272e054141cd1c890608981722d1a249f474a
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+++ b/ui/accessibility/ax_range.h
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+// 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_RANGE_H_
+#define UI_ACCESSIBILITY_AX_RANGE_H_
+
+#include "ui/accessibility/ax_position.h"
+
+namespace ui {
+
+// A range of ax positions.
+struct AX_EXPORT AXRange {
+  AXRange() : anchor(AXPosition::CreateNullPosition()), focus(AXPosition::CreateNullPosition()) {
+  }
+
+  AXRange(AXPosition anchor, AXPosition focus)
+      : anchor(anchor), focus(focus) {
+  }
+
+  virtual ~AXRange() {
+  }
+
+  bool IsNull() const { return anchor.IsNullPosition() || focus.IsNullPosition(); }
+
+  AXPosition anchor;
+  AXPosition focus;
+};
+
+}  // namespace ui
+
+#endif  // UI_ACCESSIBILITY_AX_RANGE_H_