Creates AXPosition to uniquely identify a position in the accessibility tree

ui/accessibility/ax_node.h

Index: ui/accessibility/ax_node.h
diff --git a/ui/accessibility/ax_node.h b/ui/accessibility/ax_node.h
index e1415910c8275c7d09ea887fd9370d25b2c9c82b..29ad119a7913efdcfb17aa6e8bf120e54f07c3ee 100644
--- a/ui/accessibility/ax_node.h
+++ b/ui/accessibility/ax_node.h
@@ -10,6 +10,7 @@
 #include <vector>
 
 #include "ui/accessibility/ax_node_data.h"
+#include "ui/accessibility/ax_position.h"
 
 namespace gfx {
 class Rect;
@@ -20,6 +21,8 @@ namespace ui {
 // One node in an AXTree.
 class AX_EXPORT AXNode {
  public:
+  using AXPosition = AXNodePosition;
+
   // The constructor requires a parent, id, and index in parent, but
   // the data is not required. After initialization, only index_in_parent
   // is allowed to change, the others are guaranteed to never change.