MacViews/a11y: Implement NativeViewAccessibilityMac.

ui/views/accessibility/native_view_accessibility_mac.mm

+// 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/views/accessibility/native_view_accessibility_mac.h"
+
+#include "ui/views/view.h"
+#include "ui/views/widget/widget.h"
+
+namespace views {
+
+// static
+NativeViewAccessibility* NativeViewAccessibility::Create(View* view) {
+  return new NativeViewAccessibilityMac(view);
+}
+
+NativeViewAccessibilityMac::NativeViewAccessibilityMac(View* view)
+    : NativeViewAccessibility(view) {}
+
+gfx::NativeViewAccessible NativeViewAccessibilityMac::GetParent() {
+  if (view_->parent())
+    return view_->parent()->GetNativeViewAccessible();
+
+  if (view_->GetWidget())
+    return view_->GetWidget()->GetNativeView();
+
+  if (parent_widget_)
+    return parent_widget_->GetRootView()->GetNativeViewAccessible();
+
+  return nullptr;
+}
+
+}  // namespace views