Uses the activedescendant_changed event received from Blink to fire the right focus event

content/browser/accessibility/browser_accessibility.cc

 // Copyright (c) 2012 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.
 
 #include "content/browser/accessibility/browser_accessibility.h"
 
 #include <stddef.h>
 
 #include <algorithm>
 
@@ skipping 113 matching lines @@
 }
 
 bool BrowserAccessibility::IsTextOnlyObject() const {
   return GetRole() == ui::AX_ROLE_STATIC_TEXT ||
          GetRole() == ui::AX_ROLE_LINE_BREAK ||
          GetRole() == ui::AX_ROLE_INLINE_TEXT_BOX;
 }
 
 BrowserAccessibility* BrowserAccessibility::PlatformGetChild(
     uint32_t child_index) const {
-  DCHECK_LT(child_index, PlatformChildCount());
   BrowserAccessibility* result = nullptr;
 
-  if (HasIntAttribute(ui::AX_ATTR_CHILD_TREE_ID)) {
+  if (child_index == 0 && HasIntAttribute(ui::AX_ATTR_CHILD_TREE_ID)) {
     BrowserAccessibilityManager* child_manager =
         BrowserAccessibilityManager::FromID(
             GetIntAttribute(ui::AX_ATTR_CHILD_TREE_ID));
     if (child_manager && child_manager->GetRoot()->GetParent() == this)
       result = child_manager->GetRoot();
   } else {
     result = InternalGetChild(child_index);
   }
 
   return result;
@@ skipping 1023 matching lines @@
       break;
 
     manager = root->GetParent()->manager();
     root = manager->GetRoot();
   }
 
   return bounds;
 }
 
 }  // namespace content