Fix Mac accessibility window attribute inside child frames.

content/browser/accessibility/browser_accessibility_cocoa.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 <execinfo.h>
 #include <stddef.h>
 #include <stdint.h>
 
 #import "content/browser/accessibility/browser_accessibility_cocoa.h"
 
@@ skipping 1138 matching lines @@
 - (id)parent {
   if (![self instanceActive])
     return nil;
   // A nil parent means we're the root.
   if (browserAccessibility_->GetParent()) {
     return NSAccessibilityUnignoredAncestor(
         ToBrowserAccessibilityCocoa(browserAccessibility_->GetParent()));
   } else {
     // Hook back up to RenderWidgetHostViewCocoa.
     BrowserAccessibilityManagerMac* manager =
-        static_cast<BrowserAccessibilityManagerMac*>(
-            browserAccessibility_->manager());
-    return manager->parent_view();
+        browserAccessibility_->manager()->GetRootManager()
+            ->ToBrowserAccessibilityManagerMac();
+    if (manager)
+      return manager->parent_view();
+    return nil;
   }
 }
 
 - (NSValue*)position {
   if (![self instanceActive])
     return nil;
   NSPoint origin = [self origin];
   NSSize size = [[self size] sizeValue];
   NSPoint pointInScreen = [self pointInScreen:origin size:size];
   return [NSValue valueWithPoint:pointInScreen];
@@ skipping 685 matching lines @@
     return nil;
   return [NSNumber numberWithBool:
       GetState(browserAccessibility_, ui::AX_STATE_VISITED)];
 }
 
 - (id)window {
   if (![self instanceActive])
     return nil;
 
   BrowserAccessibilityManagerMac* manager =
-      static_cast<BrowserAccessibilityManagerMac*>(
-          browserAccessibility_->manager());
+      browserAccessibility_->manager()->GetRootManager()
+          ->ToBrowserAccessibilityManagerMac();
   if (!manager || !manager->parent_view())
     return nil;
 
   return [manager->parent_view() window];
 }
 
 - (NSString*)methodNameForAttribute:(NSString*)attribute {
   return [attributeToMethodNameMap objectForKey:attribute];
 }
 
@@ skipping 734 matching lines @@
   if (![self instanceActive])
     return [super hash];
   return browserAccessibility_->GetId();
 }
 
 - (BOOL)accessibilityShouldUseUniqueId {
   return YES;
 }
 
 @end