Creates AXPosition to uniquely identify a position in the accessibility tree

content/browser/accessibility/ax_platform_position.h

Index: content/browser/accessibility/ax_platform_position.h
diff --git a/content/browser/accessibility/ax_platform_position.h b/content/browser/accessibility/ax_platform_position.h
new file mode 100644
index 0000000000000000000000000000000000000000..f8b28e58ab9a60f9311f7663dc56fdd10a983d3a
--- /dev/null
+++ b/content/browser/accessibility/ax_platform_position.h
@@ -0,0 +1,38 @@
+// 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 CONTENT_BROWSER_ACCESSIBILITY_AX_PLATFORM_POSITION_H_
+#define CONTENT_BROWSER_ACCESSIBILITY_AX_PLATFORM_POSITION_H_
+
+#include <stdint.h>
+
+#include "content/browser/accessibility/ax_tree_id_registry.h"
+#include "content/browser/accessibility/browser_accessibility.h"
+#include "ui/accessibility/ax_position.h"
+
+namespace content {
+
+using AXTreeID = content::AXTreeIDRegistry::AXTreeID;
+
+class AXPlatformPosition
+    : public ui::AXPosition<AXPlatformPosition, BrowserAccessibility> {
+ public:
+  AXPlatformPosition();
+  ~AXPlatformPosition() override;
+
+ protected:
+  void AnchorChild(int child_index,
+                   AXTreeID* tree_id,
+                   int32_t* child_id) const override;
+  int AnchorChildCount() const override;
+  int AnchorIndexInParent() const override;
+  void AnchorParent(AXTreeID* tree_id, int32_t* parent_id) const override;
+  BrowserAccessibility* GetNodeInTree(AXTreeID tree_id,
+                                      int32_t node_id) const override;
+  int MaxTextOffset() const override;
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_ACCESSIBILITY_AX_PLATFORM_POSITION_H_