8208747: [a11y] [macos] In Optionpane Demo, inside ComponentDialog Example, unable to navigate to all items, with VO on

Reviewed-by: pbansal

Author: Alexander Zuev

src/java.desktop/macosx/native/libawt_lwawt/awt/JavaComponentAccessibility.m

@@ -896,6 +896,14 @@ - (BOOL)accessibilityIsIndexAttributeSettable
     return NO;
 }
 
+- (NSInteger)accessibilityIndex {
+    int index = 0;
+    if (fParent != NULL) {
+        index = [fParent accessibilityIndexOfChild:self];
+    }
+    return index;
+}
+
 /*
  * The java/lang/Number concrete class could be for any of the Java primitive
  * numerical types or some other subclass.