a11y: Exclude children of nested keyboard accessible controls from a11y tree.

ui/accessibility/platform/ax_platform_node_mac.mm

Index: ui/accessibility/platform/ax_platform_node_mac.mm
diff --git a/ui/accessibility/platform/ax_platform_node_mac.mm b/ui/accessibility/platform/ax_platform_node_mac.mm
index 989b5b9f3181b9e3657c137590962bc71723204c..877f81958ad4576b86beb801ef946a76faf236b4 100644
--- a/ui/accessibility/platform/ax_platform_node_mac.mm
+++ b/ui/accessibility/platform/ax_platform_node_mac.mm
@@ -296,8 +296,10 @@ void NotifyMacEvent(AXPlatformNodeCocoa* target, ui::AXEvent event_type) {
 
 - (id)accessibilityHitTest:(NSPoint)point {
   for (AXPlatformNodeCocoa* child in [self AXChildren]) {
-    if (NSPointInRect(point, child.boundsInScreen))
+    if (![child accessibilityIsIgnored] &&
+        NSPointInRect(point, [child boundsInScreen])) {
       return [child accessibilityHitTest:point];
+    }
   }
   return NSAccessibilityUnignoredAncestor(self);
 }