Upstream Chrome on iOS source code [8/11].

ios/chrome/browser/ui/stack_view/close_button.mm

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#import "ios/chrome/browser/ui/stack_view/close_button.h"
+
+#include "base/logging.h"
+
+@implementation CloseButton {
+  id _accessibilityTarget;  // weak
+  SEL _accessibilityAction;
+}
+
+- (void)addAccessibilityElementFocusedTarget:(id)accessibilityTarget
+                                      action:(SEL)accessibilityAction {
+  DCHECK(!accessibilityTarget ||
+         [accessibilityTarget respondsToSelector:accessibilityAction]);
+  _accessibilityTarget = accessibilityTarget;
+  _accessibilityAction = accessibilityAction;
+}
+
+- (void)accessibilityElementDidBecomeFocused {
+  [_accessibilityTarget performSelector:_accessibilityAction withObject:self];
+}
+
+@end