Rewrite scoped_ptr<T>(NULL) to use the default ctor.

chrome/browser/ui/app_list/app_list_service_mac.mm

 // Copyright 2013 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 <ApplicationServices/ApplicationServices.h>
 #import <Cocoa/Cocoa.h>
 
 #include "apps/app_shim/app_shim_handler_mac.h"
 #include "base/bind.h"
 #include "base/command_line.h"
@@ skipping 230 matching lines @@
       profile, extension, NEW_FOREGROUND_TAB));
 }
 
 void AppListServiceMac::CreateAppList(Profile* requested_profile) {
   if (profile() == requested_profile)
     return;
 
   // The Objective C objects might be released at some unknown point in the
   // future, so explicitly clear references to C++ objects.
   [[window_controller_ appListViewController]
-      setDelegate:scoped_ptr<app_list::AppListViewDelegate>(NULL)];
+      setDelegate:scoped_ptr<app_list::AppListViewDelegate>()];
 
   SetProfile(requested_profile);
   scoped_ptr<app_list::AppListViewDelegate> delegate(
       new AppListViewDelegate(new AppListControllerDelegateCocoa(), profile()));
   window_controller_.reset([[AppListWindowController alloc] init]);
   [[window_controller_ appListViewController] setDelegate:delegate.Pass()];
 }
 
 void AppListServiceMac::Init(Profile* initial_profile) {
   // On Mac, Init() is called multiple times for a process: any time there is no
@@ skipping 187 matching lines @@
 
 // static
 AppListService* AppListService::Get() {
   return AppListServiceMac::GetInstance();
 }
 
 // static
 void AppListService::InitAll(Profile* initial_profile) {
   Get()->Init(initial_profile);
 }