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

ui/views/accessibility/native_view_accessibility.h

 // Copyright (c) 2013 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.
 
 #ifndef UI_VIEWS_ACCESSIBILITY_NATIVE_VIEW_ACCESSIBILITY_H_
 #define UI_VIEWS_ACCESSIBILITY_NATIVE_VIEW_ACCESSIBILITY_H_
 
 #include <memory>
 
 #include "base/macros.h"
@@ skipping 24 matching lines @@
 
 namespace views {
 
 class View;
 class Widget;
 
 class VIEWS_EXPORT NativeViewAccessibility
     : public ui::AXPlatformNodeDelegate,
       public WidgetObserver {
  public:
+  // A method for View to create a platform-specific NativeViewAccessibility
+  // instance for |view|. To retrieve the instance for |view|, use GetForView().
   static std::unique_ptr<NativeViewAccessibility> Create(View* view);
 
   ~NativeViewAccessibility() override;
 
   gfx::NativeViewAccessible GetNativeObject();
 
   void NotifyAccessibilityEvent(ui::AXEvent event_type);
 
   // Focuses or unfocuses a View.
   bool SetFocused(bool focused);
@@ skipping 13 matching lines @@
 
   // WidgetObserver
   void OnWidgetDestroying(Widget* widget) override;
 
   Widget* parent_widget() const { return parent_widget_; }
   void SetParentWidget(Widget* parent_widget);
 
  protected:
   explicit NativeViewAccessibility(View* view);
 
+  // Retrieves the NativeViewAccessibility instance for the given View. This
+  // invokes View::GetNativeViewAccessible() to ensure it exists.
+  static NativeViewAccessibility* GetForView(View* view);
+
   // Weak. Owns this.
   View* view_;
 
   // Weak. Uses WidgetObserver to clear. This is set on the root view for
   // a widget that's owned by another widget, so we can walk back up the
   // tree.
   Widget* parent_widget_;
 
  private:
   void PopulateChildWidgetVector(std::vector<Widget*>* result_child_widgets);
 
   // We own this, but it is reference-counted on some platforms so we can't use
   // a scoped_ptr. It is dereferenced in the destructor.
   ui::AXPlatformNode* ax_node_;
 
   ui::AXNodeData data_;
 
   DISALLOW_COPY_AND_ASSIGN(NativeViewAccessibility);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_ACCESSIBILITY_NATIVE_VIEW_ACCESSIBILITY_H_