How to use SkSL warmup

As of release 1.20, Flutter provides command line tools for app developers to
collect shaders that might be needed for end-users in the SkSL
(Skia Shader Language) format. The SkSL shaders can then be
packaged into the app, and get warmed up (pre-compiled)
when an end-user first opens the app, thereby reducing the compilation
jank in later animations. Use the following instructions to collect
and package the SkSL shaders:

Run the app with --cache-sksl turned on
    to capture shaders in SkSL:

    
flutter run --profile --cache-sksl
    

    If the same app has been previously run without --cache-sksl, then the
--purge-persistent-cache flag may be needed:

    
flutter run --profile --cache-sksl --purge-persistent-cache