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

ui/app_list/cocoa/app_list_window_controller_unittest.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.
 
 #import "base/mac/scoped_nsobject.h"
 #import "testing/gtest_mac.h"
 #include "ui/app_list/app_list_view_delegate.h"
 #import "ui/app_list/cocoa/app_list_view_controller.h"
 #import "ui/app_list/cocoa/app_list_window_controller.h"
 #include "ui/app_list/test/app_list_test_view_delegate.h"
@@ skipping 24 matching lines @@
   scoped_ptr<app_list::AppListViewDelegate> delegate(
       new app_list::test::AppListTestViewDelegate);
   controller_.reset([[AppListWindowController alloc] init]);
   [[controller_ appListViewController] setDelegate:delegate.Pass()];
 }
 
 void AppListWindowControllerTest::TearDown() {
   EXPECT_TRUE(controller_.get());
   [[controller_ window] close];
   [[controller_ appListViewController]
-     setDelegate:scoped_ptr<app_list::AppListViewDelegate>(NULL)];
+     setDelegate:scoped_ptr<app_list::AppListViewDelegate>()];
   controller_.reset();
   ui::CocoaTest::TearDown();
 }
 
 }  // namespace
 
 // Test showing, hiding and closing the app list window.
 TEST_F(AppListWindowControllerTest, ShowHideCloseRelease) {
   EXPECT_TRUE([controller_ window]);
   [[controller_ window] makeKeyAndOrderFront:nil];
   EXPECT_TRUE([[controller_ window] isVisible]);
   EXPECT_TRUE([[[controller_ window] contentView] superview]);
   [[controller_ window] close];  // Hide.
   EXPECT_FALSE([[controller_ window] isVisible]);
   [[controller_ window] makeKeyAndOrderFront:nil];
 }
 
 // Test that the key bound to cancel (usually Escape) asks the controller to
 // dismiss the window.
 TEST_F(AppListWindowControllerTest, DismissWithEscape) {
   [[controller_ window] makeKeyAndOrderFront:nil];
   EXPECT_EQ(0, delegate()->dismiss_count());
   [[controller_ window] cancelOperation:controller_];
   EXPECT_EQ(1, delegate()->dismiss_count());
 }