Creates AXPosition to uniquely identify a position in the accessibility tree

content/browser/accessibility/ax_platform_position.cc

Index: content/browser/accessibility/ax_platform_position.cc
diff --git a/content/browser/accessibility/ax_platform_position.cc b/content/browser/accessibility/ax_platform_position.cc
new file mode 100644
index 0000000000000000000000000000000000000000..d987a83e734cf3f1d4d32b84f4f67bd507d718e9
--- /dev/null
+++ b/content/browser/accessibility/ax_platform_position.cc
@@ -0,0 +1,40 @@
+// 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.
+
+#include "content/browser/accessibility/ax_platform_position.h"
+
+namespace content {
+
+AXPlatformPosition::AXPlatformPosition(AXTreeIDRegistry::AXTreeID tree_id, int32_t anchor_id, int child_index, int text_offset, AXPositionType type) : AXPosition(tree_id, anchor_id, offset, type) {
+}
+
+AXPlatformPosition::~AXPlatformPosition() {
+}
+
+BrowserAccessibility* AXPlatformPosition::GetPlatformNodeInTree(AXTreeIDRegistry::AXTreeID tree_id, int32-t node_id) const {
+  if (IsNullPosition())
+    return nullptr;
+
+  auto manager = BrowserAccessibilityManager::FromID(tree_id_);
+  if (!manager)
+    return nullptr;
+  return manager->GetFromID(id);
+}
+
+AXNode* AXPlatformPosition::GetNodeInTree(AXTreeIDRegistry::AXTreeID tree_id, int32-t node_id) const {
+  BrowserAccessibility* anchor = GetPlatformNodeFromID(tree_id, node_id);
+  return anchor ? anchor->node() : nullptr;
+}
+
+int AXPlatformPosition::MaxTextOffset() const {
+  if (IsNullPosition())
+    return -1;
+
+  BrowserAccessibility* anchor = GetPlatformNodeInTree(tree_id_, get_anchor_id());
+  if (!anchor)
+    return -1;
+  return static_cast<int>(anchor->GetText().length());
+}
+
+}  // namespace content