Fix Mac accessibility window attribute inside child frames.

content/browser/accessibility/browser_accessibility_manager_mac.mm

 // 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_manager_mac.h"
 
 #import "base/mac/mac_util.h"
 #import "base/mac/sdk_forward_declarations.h"
 #include "base/logging.h"
 #include "base/strings/sys_string_conversions.h"
@@ skipping 87 matching lines @@
 
 // static
 BrowserAccessibilityManager* BrowserAccessibilityManager::Create(
     const ui::AXTreeUpdate& initial_tree,
     BrowserAccessibilityDelegate* delegate,
     BrowserAccessibilityFactory* factory) {
   return new BrowserAccessibilityManagerMac(
       NULL, initial_tree, delegate, factory);
 }
 
+BrowserAccessibilityManagerMac*
+BrowserAccessibilityManager::ToBrowserAccessibilityManagerMac() {
+  return static_cast<BrowserAccessibilityManagerMac*>(this);
+}
+
 BrowserAccessibilityManagerMac::BrowserAccessibilityManagerMac(
     NSView* parent_view,
     const ui::AXTreeUpdate& initial_tree,
     BrowserAccessibilityDelegate* delegate,
     BrowserAccessibilityFactory* factory)
     : BrowserAccessibilityManager(delegate, factory),
       parent_view_(parent_view) {
   Initialize(initial_tree);
 }
 
@@ skipping 338 matching lines @@
   }
 
   return @{
     NSAccessibilityTextStateChangeTypeKey : @(AXTextStateChangeTypeEdit),
     NSAccessibilityTextChangeValues : changes,
     NSAccessibilityTextChangeElement : native_node
   };
 }
 
 }  // namespace content