Views a11y: Implement AXPlatformNode::FromNativeViewAccessible on all platforms.

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 {
 
+NativeViewAccessibilityMac::NativeViewAccessibilityMac(View* view)
+    : NativeViewAccessibility(view) {}
+
+gfx::NativeViewAccessible
+NativeViewAccessibilityMac::GetNativeViewAccessibleForWidget() {
+  if (view_->GetWidget())
+    return view_->GetWidget()->GetNativeView();
+  return NativeViewAccessibility::GetNativeViewAccessibleForWidget();
+}
+
 // 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