Initial support for accessibility actions on ARC.

ui/accessibility/ax_host_delegate.cc

+// Copyright 2017 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 "ui/accessibility/ax_host_delegate.h"
+
+#include "ui/accessibility/ax_tree_id_registry.h"
+
+namespace ui {
+
+AXHostDelegate::AXHostDelegate()
+    : tree_id_(AXTreeIDRegistry::GetInstance()->GetOrCreateAXTreeID(this)) {}
+
+AXHostDelegate::AXHostDelegate(int32_t tree_id) : tree_id_(tree_id) {
+  AXTreeIDRegistry::GetInstance()->SetDelegateForID(this, tree_id);
+}
+
+AXHostDelegate::~AXHostDelegate() {
+  AXTreeIDRegistry::GetInstance()->RemoveAXTreeID(tree_id_);
+}
+
+}  // namespace ui