[C++11 Allowed Features] Declares a type-safe null pointer converting from NULL to nullptr

content/browser/accessibility/browser_accessibility_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.
 
 #import <Cocoa/Cocoa.h>
 
 #import "content/browser/accessibility/browser_accessibility_mac.h"
 
 #import "content/browser/accessibility/browser_accessibility_cocoa.h"
 #include "content/browser/accessibility/browser_accessibility_manager_mac.h"
 
 namespace content {
 
 // Static.
 BrowserAccessibility* BrowserAccessibility::Create() {
   return new BrowserAccessibilityMac();
 }
 
 BrowserAccessibilityMac::BrowserAccessibilityMac()
-    : browser_accessibility_cocoa_(NULL) {
+    : browser_accessibility_cocoa_(nullptr) {
 }
 
 void BrowserAccessibilityMac::OnDataChanged() {
   BrowserAccessibility::OnDataChanged();
 
   if (browser_accessibility_cocoa_) {
     [browser_accessibility_cocoa_ childrenChanged];
     return;
   }
 
@@ skipping 31 matching lines @@
       initWithObject:this];
   [browser_accessibility_cocoa_ swapChildren:&children];
 }
 
 BrowserAccessibilityCocoa* BrowserAccessibility::ToBrowserAccessibilityCocoa() {
   return static_cast<BrowserAccessibilityMac*>(this)->
       native_view();
 }
 
 }  // namespace content