Migrate a Windows project to support dark title bars

Projects created before Flutter 3.7 have light title bars even when the Windows theme is dark mode. Projects created before Flutter 3.7 need to be migrated to support dark title bars.

Migration steps

Your project can be updated using these steps:

1. Verify you are on Flutter version 3.7 or newer using flutter --version
2. If needed, use flutter upgrade to update to the latest version of the Flutter SDK
3. Backup your project, possibly using git or some other version control system
4. Delete the following files:
   1. windows/runner/CMakeLists.txt
   2. windows/runner/win32_window.cpp
   3. windows/runner/win32_window.h
5. Run flutter create --platforms=windows .
6. Review the changes to the following files:
   1. windows/runner/CMakeLists.txt
   2. windows/runner/win32_window.cpp
   3. windows/runner/win32_window.h
7. Verify your app builds using flutter build windows

Example

PR 862 shows the migration work for the Flutter Gallery app.