Summary:
Standardize WS implementation for JS environments.
Why do we need a separate server implementation for browsers?
Browser targets cannot authenticate via the default certificate exchange flow. For browser targets we verify the origin instead.
Moreover, for already forgotten reasons the initial implementation of the WS server for browsers used a different kind of message structure and added extra `connect`/`disconnect` messages. After examination, it seems the `connect`/`disconnect` flow is redundant.
Major changes:
1. Updated class hierarchy for WS server implementations.
2. Updated browser WS server to support the modern and the legacy protocols.
3. Now a websocket connection with the device is closed on error. The idea is it is highly unlikely to handle any subsequent messages properly once we observe an error. It is better to bail and reconnect. What do you think?
Reviewed By: mweststrate
Differential Revision: D31532172
fbshipit-source-id: f86aa63a40efe4d5263353cc124fac8c63b80e45
