Custom progress API needs to take plugin toolkit into account.

1. If targeted toolkit is not available, the only reasonable choose is to use default Swing/AWT toolkit for rendering custom progress bar.

2. After toolkit download is completed, custom progress needs to use newly downloaded toolkit for rendering custom progress bar

3. A JVM relaunching is needed during toolkit switch, that can cause to destroy/create container/surface where custom progress bar to render to.

4. Developer may require to implement 2 custom progress bar with 2 different toolkits.