ui/views: Cleanup usage of scoped_ptr.

ui/views/test/event_generator_delegate_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 <Cocoa/Cocoa.h>
 
 #import "base/mac/scoped_objc_class_swizzler.h"
 #include "base/memory/singleton.h"
 #include "ui/events/event_processor.h"
 #include "ui/events/event_target.h"
@@ skipping 294 matching lines @@
 }
 
 EventGeneratorDelegateMac::~EventGeneratorDelegateMac() {
   DCHECK_EQ(this, ui::test::EventGenerator::default_delegate);
   ui::test::EventGenerator::default_delegate = NULL;
 }
 
 scoped_ptr<ui::EventTargetIterator>
 EventGeneratorDelegateMac::GetChildIterator() const {
   // Return NULL to dispatch all events to the result of GetRootTarget().
-  return scoped_ptr<ui::EventTargetIterator>();
+  return nullptr;
 }
 
 void EventGeneratorDelegateMac::OnMouseEvent(ui::MouseEvent* event) {
   // For mouse drag events, ensure the swizzled methods return the right flags.
   base::AutoReset<ui::test::EventGenerator*> reset(&g_active_generator, owner_);
   NSEvent* ns_event = CreateMouseEventInWindow(window_,
                                                event->type(),
                                                event->location(),
                                                event->changed_button_flags());
   if (owner_->targeting_application())
@@ skipping 32 matching lines @@
 
 namespace views {
 namespace test {
 
 void InitializeMacEventGeneratorDelegate() {
   EventGeneratorDelegateMac::GetInstance();
 }
 
 }  // namespace test
 }  // namespace views