a11y: Exclude children of nested keyboard accessible controls from a11y tree.

ui/accessibility/platform/ax_platform_node_mac.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 "ui/accessibility/platform/ax_platform_node_mac.h"
 
 #import <Cocoa/Cocoa.h>
 #include <stddef.h>
 
 #include "base/macros.h"
@@ skipping 266 matching lines @@
 }
 
 // NSAccessibility informal protocol implementation.
 
 - (BOOL)accessibilityIsIgnored {
   return [[self AXRole] isEqualToString:NSAccessibilityUnknownRole];
 }
 
 - (id)accessibilityHitTest:(NSPoint)point {
   for (AXPlatformNodeCocoa* child in [self AXChildren]) {
-    if (NSPointInRect(point, child.boundsInScreen))
+    if (NSPointInRect(point, [child boundsInScreen]) &&
+        ![child accessibilityIsIgnored])
       return [child accessibilityHitTest:point];
   }
   return NSAccessibilityUnignoredAncestor(self);
 }
 
 - (BOOL)accessibilityNotifiesWhenDestroyed {
   return YES;
 }
 
 - (id)accessibilityFocusedUIElement {
@@ skipping 297 matching lines @@
   }
   NotifyMacEvent(native_node_, event_type);
 }
 
 int AXPlatformNodeMac::GetIndexInParent() {
   // TODO(dmazzoni): implement this.  http://crbug.com/396137
   return -1;
 }
 
 }  // namespace ui