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

chrome/browser/ui/gtk/custom_button.cc

 // 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.
 
 #include "chrome/browser/ui/gtk/custom_button.h"
 
 #include "base/basictypes.h"
 #include "base/debug/trace_event.h"
 #include "base/logging.h"
 #include "chrome/browser/ui/gtk/gtk_chrome_button.h"
@@ skipping 19 matching lines @@
     resource_id, ui::ResourceBundle::RTL_ENABLED).ToGdkPixbuf();
 }
 
 }  // namespace
 
 CustomDrawButtonBase::CustomDrawButtonBase(GtkThemeService* theme_provider,
                                            int normal_id,
                                            int pressed_id,
                                            int hover_id,
                                            int disabled_id)
-    : background_image_(NULL),
-      paint_override_(-1),
+    : paint_override_(-1),
       normal_id_(normal_id),
       pressed_id_(pressed_id),
       hover_id_(hover_id),
       disabled_id_(disabled_id),
       theme_service_(theme_provider),
       flipped_(false) {
   for (int i = 0; i < (GTK_STATE_INSENSITIVE + 1); ++i)
     surfaces_[i].reset(new gfx::CairoCachedSurface);
   background_image_.reset(new gfx::CairoCachedSurface);
 
@@ skipping 337 matching lines @@
   }
 
   gtk_chrome_button_set_use_gtk_rendering(
       GTK_CHROME_BUTTON(widget()), UseGtkTheme());
 }
 
 bool CustomDrawButton::UseGtkTheme() {
   return !forcing_chrome_theme_ && theme_service_ &&
       theme_service_->UsingNativeTheme();
 }