Fix WebSocket polyfill throwing on close()/send() when CLOSING or CLOSED

[bghgary]

[Created by Copilot on behalf of @bghgary]

Problem

The WebSocket polyfill throws JavaScript errors in two places where the WHATWG WebSocket specification requires different behavior:

close() throws when already closing/closed

WebSocket::Close throws Error: Close has already been called. when invoked on a socket whose readyState is already CLOSING or CLOSED. Per the spec, close() in those states must be a silent no-op.

send() throws when closing/closed

WebSocket::Send throws Error: Websocket readyState is not open. on any non-OPEN state. Per the spec, send() should only throw InvalidStateError when readyState is CONNECTING. When CLOSING or CLOSED, the data is silently discarded (the spec also bumps bufferedAmount, which this polyfill does not track).

Because the throws are synchronous from a JS call, a delayed or racing call from an async callback surfaces as an uncaught exception that terminates the JS runtime.

Repro path

Observed on the macOS_Xcode164_Sanitizers leg of #148. Sequence (from the existing multi-WebSocket test in Tests/UnitTests/Scripts/tests.ts):

1. Test calls ws.close() on an open socket.
2. The native side transitions readyState -> Closing and issues the close.
3. Before the onclose callback marshals to the JS thread, another path (a pending onmessage handler, or a catch block on a failed send) calls ws.close() again.
4. The second close() finds readyState == Closing and throws, producing:

[Uncaught Error] close@[native code]
@app:///Scripts/tests.js:27799:22

The send() path is symmetric: a send scheduled between close() being called and the onclose callback firing would throw and escape uncaught.

Fix

close()

Replace the throw with an early return. No other state is touched, so the first close() still drives the transition to CLOSED via the normal callback path.

send()

Split the single non-OPEN throw into two cases: throw on CONNECTING, return silently on CLOSING/CLOSED.

Scope

• Pure behavioral fix in the WebSocket polyfill. No changes outside Polyfills/WebSocket/Source/WebSocket.cpp.
• No test changes — existing WebSocket tests already exercise these paths and will stop intermittently failing once this lands.
• bufferedAmount tracking during the CLOSING/CLOSED send path is still not implemented; out of scope for this fix.

[Copilot]

Pull request overview

Adjusts the WebSocket polyfill’s close() behavior to match the WHATWG spec by making repeated calls in CLOSING/CLOSED states a silent no-op instead of throwing.

Changes:

• Make WebSocket::Close() return early (no-op) when readyState is Closing or Closed.
• Remove the synchronous JS exception previously thrown on repeated close() calls.
• Add an in-code comment documenting the spec-aligned behavior.

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