[UI Cocoa] Hide the global error bubble icon from accessibility

ui/base/cocoa/a11y_util.mm

+// Copyright 2016 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 "ui/base/cocoa/a11y_util.h"
+
+namespace ui {
+namespace a11y_util {
+
+void HideImageFromAccessibilityOrder(NSImageView* view) {
+  // This is the minimum change necessary to get VoiceOver to skip the image
+  // (instead of reading the word "image"). Accessibility mechanisms in OSX
+  // change once in a while, so this may be fragile.
+  [[view cell] accessibilitySetOverrideValue:@""
+                                forAttribute:NSAccessibilityRoleAttribute];
+}
+
+}  // namespace a11y_util
+}  // namespace ui