Creates AXPosition to uniquely identify a position in the accessibility tree

ui/accessibility/BUILD.gn

 # Copyright 2014 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.
 
 import("//build/config/linux/pkg_config.gni")
 import("//build/config/features.gni")
 import("//build/config/ui.gni")
 import("//build/json_schema_api.gni")
 import("//testing/libfuzzer/fuzzer_test.gni")
 import("//testing/test.gni")
 if (is_android) {
   import("//build/config/android/rules.gni")
 }
 
 component("accessibility") {
   sources = [
     "ax_node.cc",
     "ax_node.h",
     "ax_node_data.cc",
     "ax_node_data.h",
+    "ax_position.cc",
+    "ax_position.h",
+    "ax_range.h",
     "ax_relative_bounds.cc",
     "ax_relative_bounds.h",
     "ax_serializable_tree.cc",
     "ax_serializable_tree.h",
     "ax_text_utils.cc",
     "ax_text_utils.h",
     "ax_tree.cc",
     "ax_tree.h",
     "ax_tree_combiner.cc",
     "ax_tree_combiner.h",
@@ skipping 81 matching lines @@
     "tree_generator.h",
   ]
 
   deps = [
     ":accessibility",
   ]
 }
 
 test("accessibility_unittests") {
   sources = [
     "ax_generated_tree_unittest.cc",

[dmazzoni, 2016/10/05 18:15:30]

I think you need to add ax_position_unittest here

     "ax_text_utils_unittest.cc",
     "ax_tree_combiner_unittest.cc",
     "ax_tree_serializer_unittest.cc",
     "ax_tree_unittest.cc",
     "platform/ax_platform_node_win_unittest.cc",
   ]
 
   deps = [
     ":accessibility",
     ":test_support",
@@ skipping 24 matching lines @@
 
 fuzzer_test("ax_tree_fuzzer") {
   sources = [
     "ax_tree_fuzzer.cc",
   ]
 
   deps = [
     ":accessibility",
   ]
 }