Remove all uses of toolkit_use_gtk in the gyp files.

ui/gfx/gdk_compat.h

-// 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.
-
-#ifndef UI_GFX_GDK_COMPAT_H_
-#define UI_GFX_GDK_COMPAT_H_
-
-#include <gtk/gtk.h>
-#include <gdk/gdkx.h>
-
-// Google Chrome must depend on GTK 2.18, at least until the next LTS drops
-// (and we might have to extend which version of GTK we want to target due to
-// RHEL). To make our porting job for GTK3 easier, we define all the methods
-// that replace deprecated APIs in this file and then include it everywhere.
-//
-// This file is organized first by version, and then with each version,
-// alphabetically by method.
-
-#if !GTK_CHECK_VERSION(2, 24, 0)
-inline GdkWindow* gdk_x11_window_lookup_for_display(GdkDisplay* display,
-                                                    Window window) {
-  return static_cast<GdkWindow*>(gdk_xid_table_lookup_for_display(display,
-                                                                  window));
-}
-#endif
-
-#endif  // UI_GFX_GDK_COMPAT_H_