Here you go: https://chrome.google.com/webstore/detail/cheerpj-applet-run...
CheerpJ does exactly that: it ships a full JVM implementation (including Swing/AWT, Threads, ...) that runs in JS/Wasm inside your browser. The Applet Runner extension detects applets in the page and runs them through CheerpJ.
The example that you list seems to work.