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
new file mode 100644
index 0000000000000000000000000000000000000000..aab80bddc8eed3d2023a58285ad149e83e4d5652
--- /dev/null
+++ b/ui/accessibility/ax_range.h
@@ -0,0 +1,33 @@
+// 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_
+
+namespace ui {
+
+// A range of ax positions.
+template <AXPositionType>
+struct AXRange {
+  AXRange()
+      : anchor(AXPositionType::CreateNullPosition()),
+        focus(AXPositionType::CreateNullPosition()) {}
+
+  AXRange(AXPositionType* anchor, AXPositionType* focus)
+      : anchor(anchor), focus(focus) {}
+
+  virtual ~AXRange() {}
+
+  bool IsNull() const {
+    return !anchor || !focus || anchor->IsNullPosition() ||
+           focus->IsNullPosition();
+  }
+
+  AXPositionType* anchor;
+  AXPositionType* focus;
+};
+
+}  // namespace ui
+
+#endif  // UI_ACCESSIBILITY_AX_RANGE_H_