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..c221cbf86a2dc49eb76e4c03bb79354fcb0af4af
--- /dev/null
+++ b/content/browser/accessibility/ax_platform_position.cc
@@ -0,0 +1,76 @@
+// 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,
+    ui::AXPositionType type,
+    std::unique_ptr<ui::AXPositionFactory> factory)
+    : ui::AXPosition(tree_id,
+                     anchor_id,
+                     child_index,
+                     text_offset,
+                     type,
+                     factory) {}
+
+AXPlatformPosition::~AXPlatformPosition() {}
+
+ui::AXPosition AXPlatformPositionFactory::CreateNullPosition() {
+  return AXPlatformPosition(-1 /* tree_id */, -1 /* anchor_id */,
+                            -1 /* child_index */, -1 /* text_offset */,
+                            ui::AXPositionType::NullPosition);
+}
+
+ui::AXPosition AXPlatformPositionFactory::CreateTreePosition(int tree_id,
+                                                             int32_t anchor_id,
+                                                             int child_index) {
+  return AXPlatformPosition(tree_id, anchor_id, child_index,
+                            -1 /* text_offset */,
+                            ui::AXPositionType::TreePosition);
+}
+
+ui::AXPosition AXPlatformPositionFactory::CreateTextPosition(int tree_id,
+                                                             int32_t anchor_id,
+                                                             int text_offset) {
+  return AXPlatformPosition(tree_id, anchor_id, -1 /* child_index */,
+                            text_offset, ui::AXPositionType::TextPosition);
+}
+
+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(node_id);
+}
+
+ui::AXNode* AXPlatformPosition::GetNodeInTree(
+    AXTreeIDRegistry::AXTreeID tree_id,
+    int32_t node_id) const {
+  BrowserAccessibility* anchor = GetPlatformNodeInTree(tree_id, node_id);
+  return anchor ? anchor->node() : nullptr;
+}
+
+int AXPlatformPosition::MaxTextOffset() const {
+  if (IsNullPosition())
+    return -1;
+
+  BrowserAccessibility* anchor =
+      GetPlatformNodeInTree(get_tree_id(), get_anchor_id());
+  if (!anchor)
+    return -1;
+  return static_cast<int>(anchor->GetText().length());
+}
+
+}  // namespace content