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

ui/views/view.h

Index: ui/views/view.h
diff --git a/ui/views/view.h b/ui/views/view.h
index fcbee85c1bf2155eef7639c5b96e75c6980c1b4f..f68358bcd4fd8cf6e15424364e5ead38e2d5d743 100644
--- a/ui/views/view.h
+++ b/ui/views/view.h
@@ -36,6 +36,7 @@
 #include "ui/gfx/geometry/vector2d.h"
 #include "ui/gfx/native_widget_types.h"
 #include "ui/gfx/path.h"
+#include "ui/views/accessibility/native_view_accessibility.h"
 #include "ui/views/view_targeter.h"
 #include "ui/views/views_export.h"
 
@@ -72,7 +73,6 @@ class DragController;
 class FocusManager;
 class FocusTraversable;
 class LayoutManager;
-class NativeViewAccessibility;
 class ScrollView;
 class ViewObserver;
 class Widget;
@@ -1259,6 +1259,9 @@ class VIEWS_EXPORT View : public ui::LayerDelegate,
   friend class internal::RootView;
   friend class internal::ScopedChildrenLock;
   friend class FocusManager;
+#if !defined(PLATFORM_HAS_NATIVE_VIEW_ACCESSIBILITY_IMPL)
+  friend class NativeViewAccessibility;
+#endif
   friend class ViewLayerTest;
   friend class Widget;
 
@@ -1616,9 +1619,8 @@ class VIEWS_EXPORT View : public ui::LayerDelegate,
 
   // Accessibility -------------------------------------------------------------
 
-  // Belongs to this view, but it's reference-counted on some platforms
-  // so we can't use a scoped_ptr. It's dereferenced in the destructor.
-  NativeViewAccessibility* native_view_accessibility_;
+  // The accessibility element used to represent this View.
+  std::unique_ptr<NativeViewAccessibility> native_view_accessibility_;
 
   // Observers -------------------------------------------------------------