Record WebGL separately

[rafern]

• we can't allow some callbacks to "pass through" (be executed normally), since that will have side-effects and the JS state is not recording, meaning that the "passed-through" function call might have a different effect than when it was recorded
• the only way to make "pass-through" callbacks work would be to individually patch them via a config file, which would be a nightmare to maintain
• since WebGL is the only user-visible engine output, it's the only side-effect we need to record