Re: [fetch] Introduce convenience property for request's context (#93)

1. Let's assume Chrome can change.

2. I agree with @annevk that we need more granularity in the `ResourceType` enum. For instance, `image` is "optionally-blockable" for the purposes of mixed content, while "imageset" is blockable. Likewise, `track` is blocked, while `audio` and `video` are optionally-blocked. Splitting these out allows us to be more aggressive about blocking things than we could be otherwise.

3. It's not clear to me what distinctions `Initiator` is meant to express. It's also not clear that it gives us enough data to replicate `connect-src`, but whatever. We can figure that out.

---
Reply to this email directly or view it on GitHub:
https://github.com/whatwg/fetch/issues/93#issuecomment-125962302