How to take a screenshot with Unity WebGPU?

AsyncCapture.cs

// https://discussions.unity.com/t/how-to-take-a-screenshot-with-unity-webgpu/1681498/2

using System.Runtime.InteropServices;
using Unity.Collections;
using UnityEngine;
using UnityEngine.Rendering;

public sealed class AsyncCapture : MonoBehaviour
{
    // ProcessCapture is defined in ASyncCapture.jslib
    [DllImport("__Internal")]
    private static extern void ProcessCapture(byte[] pngPtr, int pngLength);

    int frameCount = 0;

    void Update()
    {
        // Capture on the 10th frame, an arbitrarily picked frame
        frameCount++;
        if (frameCount == 10)
        {
            var (w, h) = (Screen.width, Screen.height);
            var (scale, offs) = (new Vector2(1, -1), new Vector2(0, 1));
            var grabRT = new RenderTexture(w, h, 0);
            var flipRT = new RenderTexture(w, h, 0);
            var rtFormat = grabRT.graphicsFormat;

            // Capture the screen to grabRT. This will be upside down, so we'll need to flip it.
            ScreenCapture.CaptureScreenshotIntoRenderTexture(grabRT);
            // Flip grabRT by blit'ing it to flipRT with a -1 y scale
            Graphics.Blit(grabRT, flipRT, scale, offs); // flip Y

            // Read the contents of flipRT to CPU memory. WebGPU does not support synchronous
            // readback, so we need to use async readback.
            AsyncGPUReadback.Request(flipRT, 0, TextureFormat.RGBA32, (req) =>
            {
                // We don't need these textures anymore.
                DestroyImmediate(grabRT);
                DestroyImmediate(flipRT);

                // Get the image memory we just read
                var imageData = req.GetData<byte>().ToArray();

                // Encode the image to a PNG
                byte[] pngData = ImageConversion.EncodeArrayToPNG(imageData, UnityEngine.Experimental.Rendering.GraphicsFormat.R8G8B8A8_UNorm, (uint)w, (uint)h);

                // Send the PNG data to JavaScript to do something with it
                ProcessCapture(pngData, pngData.Length);
            });
        }
    }
}

AsyncCapture.jslib

mergeInto(LibraryManager.library, {
  ProcessCapture: function(pngPtr, pngLength) {
    // Get the JS view of the Wasm memory
    const pngBytes = new Uint8Array(Module.HEAPU8.buffer, pngPtr, pngLength);
    // Create a PNG Blob for the png data
    const imageBlob = new Blob([pngBytes], { type: 'image/png' });
    // Create an Object URL from the PNG blob
    const imageUrl = URL.createObjectURL(imageBlob);

    // Create an Image element to display the PNG Object URL and add it to the page
    const imageElement = document.createElement('img');
    imageElement.src = imageUrl;
    document.body.appendChild(imageElement);
  }
});