Gtk: Change NULL to nullptr

chrome/browser/ui/libgtkui/native_theme_gtk3.cc

 // Copyright 2016 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/libgtkui/native_theme_gtk3.h"
 
 #include <gtk/gtk.h>
 
 #include "chrome/browser/ui/libgtkui/chrome_gtk_frame.h"
 #include "chrome/browser/ui/libgtkui/chrome_gtk_menu_subclasses.h"
@@ skipping 521 matching lines @@
   };
   if (GtkVersionCheck(3, 20)) {
     auto context = GetStyleContextFromCss(
         "GtkMenu#menu GtkSeparator#separator.horizontal");
     GtkBorder margin, border, padding;
     GtkStateFlags state = gtk_style_context_get_state(context);
     gtk_style_context_get_margin(context, state, &margin);
     gtk_style_context_get_border(context, state, &border);
     gtk_style_context_get_padding(context, state, &padding);
     int min_height = 1;
-    gtk_style_context_get(context, state, "min-height", &min_height, NULL);
+    gtk_style_context_get(context, state, "min-height", &min_height, nullptr);
     int w = rect.width() - margin.left - margin.right;
     int h = std::max(
         min_height + padding.top + padding.bottom + border.top + border.bottom,
         1);
     int x = margin.left;
     int y = separator_offset(h);
     PaintWidget(canvas, gfx::Rect(x, y, w, h), context, BG_RENDER_NORMAL, true);
   } else {
     auto context = GetStyleContextFromCss(
         "GtkMenu#menu GtkMenuItem#menuitem.separator.horizontal");
@@ skipping 38 matching lines @@
 
   if (frame_top_area.incognito) {
     bitmap = SkBitmapOperations::CreateHSLShiftedBitmap(
         bitmap, kDefaultTintFrameIncognito);
   }
 
   canvas->drawBitmap(bitmap, rect.x(), rect.y());
 }
 
 }  // namespace libgtkui