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

ui/views/accessibility/native_view_accessibility.cc

Index: ui/views/accessibility/native_view_accessibility.cc
diff --git a/ui/views/accessibility/native_view_accessibility.cc b/ui/views/accessibility/native_view_accessibility.cc
index f2efa2ef34db7a82b4e348aafbe5c14becf4a8b6..8a6694df402206df6092a5ec5c3a60f055cea425 100644
--- a/ui/views/accessibility/native_view_accessibility.cc
+++ b/ui/views/accessibility/native_view_accessibility.cc
@@ -6,6 +6,7 @@
 
 #include "base/memory/ptr_util.h"
 #include "base/strings/utf_string_conversions.h"
+#include "ui/accessibility/platform/ax_platform_node.h"
 #include "ui/events/event_utils.h"
 #include "ui/gfx/native_widget_types.h"
 #include "ui/views/controls/native/native_view_host.h"
@@ -19,8 +20,7 @@ namespace views {
 std::unique_ptr<NativeViewAccessibility> NativeViewAccessibility::Create(
     View* view) {
   // Use WrapUnique over MakeUnique to invoke the protected constructor.
-  return base::WrapUnique<NativeViewAccessibility>(
-      new NativeViewAccessibility(view));
+  return base::WrapUnique(new NativeViewAccessibility(view));
 }
 #endif  // !defined(PLATFORM_HAS_NATIVE_VIEW_ACCESSIBILITY_IMPL)
 
@@ -241,6 +241,25 @@ void NativeViewAccessibility::SetParentWidget(Widget* parent_widget) {
   parent_widget_->AddObserver(this);
 }
 
+// static
+NativeViewAccessibility* NativeViewAccessibility::GetForView(View* view) {
+#if defined(PLATFORM_HAS_NATIVE_VIEW_ACCESSIBILITY_IMPL)
+  // Retrieving the gfx::NativeViewAccessible also ensures that a
+  // NativeViewAccessibility exists for the given View.
+  gfx::NativeViewAccessible native_object = view->GetNativeViewAccessible();
+  ui::AXPlatformNode* node =
+      ui::AXPlatformNode::FromNativeViewAccessible(native_object);
+  DCHECK(node);
+  return static_cast<NativeViewAccessibility*>(node->GetDelegate());
+#else
+  // Platforms (currently ChromeOS) without a native implementation also have no
+  // gfx::NativeViewAccessible, so make sure a NativeViewAccessibility exists
+  // and return the instance belonging to |view|.
+  view->GetNativeViewAccessible();
+  return view->native_view_accessibility_.get();
+#endif
+}
+
 void NativeViewAccessibility::PopulateChildWidgetVector(
     std::vector<Widget*>* result_child_widgets) {
   // Only attach child widgets to the root view.