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 7c49cd0444346d7291793796970f16a6d7a7c505..6b34a4af9919308120065bdb4a4e0c54b7e79a40 100644
--- a/ui/views/cocoa/bridged_content_view.mm
+++ b/ui/views/cocoa/bridged_content_view.mm
@@ -10,6 +10,7 @@
 #import "base/mac/sdk_forward_declarations.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"
@@ -1421,9 +1422,14 @@ NSAttributedString* GetAttributedString(
 // 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];
 }