[web:tool] update --web-renderer option to account for html deprecation, and wasm support

[stoneLee81]

Document Link

https://docs.flutter.dev/platform-integration/web/wasm

What problem are you solving?

The command flutter build web --web-renderer auto can automatically select between html and canvaskit based on the environment. With the new Flutter version 3.22.0, Flutter Web now supports WASM. If I want the compiled web to adapt to the environment and automatically select between html, canvaskit, and wasm, can I also use the --web-renderer auto command?

[yjbanov]

I'll take this issue as a general request for updating our web-renderer options. Two things are happening roughly in parallel, the html renderer deprecation, and introduction of wasm/skwasm. Wasm/skwasm adapts to the environment automatically. Currently, we fallback to CanvasKit because we have to fall back from both WasmGC and multi-threaded rendering at the same time.

[mdebbar]

The HTML renderer has been removed completely, as well as the auto renderer option.

To select dynamically between CanvasKit and Skwasm, you can use the --wasm option to build both, and then select at runtime using the renderer option in index.html. For more info: https://docs.flutter.dev/platform-integration/web/renderers