websocket: reduce memory usage

[tsctx]

> $ node memory.js // before memoryUsage: 104Kib > $ node memory.js // after memoryUsage: 68Kib

const socket = new WebSocket("ws://localhost:5001") socket.onopen = function () { const rss = process.memoryUsage.rss() socket.send("hi") socket.onmessage = function () { console.log(`memoryUsage: ${(process.memoryUsage.rss() - rss) / 1024}Kib`) socket.close() } }

Refs: websockets/ws@ddfe4a8

[tsctx]

It is effective because it can greatly reduce memory at the same performance.

[mcollina]

lgtm