Add support for passing an option bag (WebSocketInit dictionary) as the second argument to the WebSocket constructor. The option bag will initially support a "protocols" option, allowing developers to specify subprotocols (mirroring the existing protocols argument), and also serves as an extension point for future options. Before, this would be written `const socket = new WebSocket("wss://example.com:8080", "soap")`. After, this could also be written `const socket = new WebSocket("wss://example.com:8080", { protocols: "soap" })`. See https://github.com/whatwg/websockets/issues/42 and spec PR https://github.com/whatwg/websockets/pull/76 for this change.
There is a demand for extensibility of options on the WebSocket constructor, to mirror the "option bag" approach that the Fetch API has. https://github.com/whatwg/websockets/issues/42 is requested by a number of implementors and users, and Chromium wants this as a means to add a `targetAddressSpace` option matching the one added to Fetch for Local Network Access (https://wicg.github.io/local-network-access/#fetch-api).
Explainers: https://github.com/whatwg/websockets/issues/42 https://github.com/whatwg/websockets/pull/76