feat: honor nativeTheme.themeSource = 'dark' before creating BrowserWindow on Windows (#25373)

* fix: support 'dark' theme before creating windows.

shell/browser/win/dark_mode.h

@@ -0,0 +1,28 @@
+// Copyright (c) 2020 Microsoft Inc. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE-CHROMIUM file.
+
+#ifndef SHELL_BROWSER_WIN_DARK_MODE_H_
+#define SHELL_BROWSER_WIN_DARK_MODE_H_
+
+#ifdef WIN32_LEAN_AND_MEAN
+#include <Windows.h>
+#else
+#define WIN32_LEAN_AND_MEAN
+#include <Windows.h>
+#undef WIN32_LEAN_AND_MEAN
+#endif
+
+#include "ui/native_theme/native_theme.h"
+
+namespace electron {
+
+namespace win {
+
+void SetDarkModeForWindow(HWND hWnd, ui::NativeTheme::ThemeSource theme_source);
+
+}  // namespace win
+
+}  // namespace electron
+
+#endif  // SHELL_BROWSER_WIN_DARK_MODE_H_