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

ui/views/cocoa/bridged_content_view.mm

Index: ui/views/cocoa/bridged_content_view.mm
diff --git a/ui/views/cocoa/bridged_content_view.mm b/ui/views/cocoa/bridged_content_view.mm
index 1623e32b8ede82ff2b578ad5500010dca09f991c..b21c51210b907b59eef30675067f0ac4b4505461 100644
--- a/ui/views/cocoa/bridged_content_view.mm
+++ b/ui/views/cocoa/bridged_content_view.mm
@@ -9,6 +9,7 @@
 #import "base/mac/scoped_nsobject.h"
 #include "base/strings/sys_string_conversions.h"
 #include "skia/ext/skia_utils_mac.h"
+#import "ui/accessibility/platform/ax_platform_node_mac.h"
 #include "ui/base/cocoa/cocoa_base_utils.h"
 #include "ui/base/dragdrop/drag_drop_types.h"
 #include "ui/base/dragdrop/os_exchange_data_provider_mac.h"
@@ -1351,9 +1352,14 @@ ui::KeyEvent GetCharacterEventFromNSEvent(NSEvent* event) {
 // NSAccessibility informal protocol implementation.
 
 - (id)accessibilityAttributeValue:(NSString*)attribute {
-  if ([attribute isEqualToString:NSAccessibilityChildrenAttribute]) {
-    return @[ hostedView_->GetNativeViewAccessible() ];
-  }
+  if ([attribute isEqualToString:NSAccessibilityChildrenAttribute])
+    return [((AXPlatformNodeCocoa*)hostedView_->GetNativeViewAccessible())
+        accessibilityAttributeValue:attribute];
+  else if ([attribute isEqualToString:NSAccessibilityParentAttribute])
+    // BridgedContentView is the top level for Views in a Widget.
+    return self;
+  else if ([attribute isEqualToString:NSAccessibilityRoleAttribute])
+    return NSAccessibilityWindowRole;
 
   return [super accessibilityAttributeValue:attribute];
 }