Initial fetch refactor

[KiChjang]

Partial #4576
I am really unsure of how things would look like, so would really appreciate some feedback on this.

[bors-servo]

☔ The latest upstream changes (presumably #7265) made this pull request unmergeable. Please resolve the merge conflicts.

[jdm]

This is a good start! Having looked further at the fetch spec and the existing code, I propose the following:

• we should only require the FetchContext value when we go to the network in http_network_or_cache_fetch (which obviously is not actually implemented yet).
• spawn a thread in fetch_async, call fetch from it, and invoke listener.response_available with the Response return value

fetch_async now runs asynchronously from the point of view of the caller, and the listener will need to be implemented such that it sends the Response value that is passed over a channel back to the thread that invoked fetch_async (just like http://mxr.mozilla.org/servo/source/components/script/network_listener.rs#16)

Does that make sense?

[bors-servo]

☔ The latest upstream changes (presumably #7710) made this pull request unmergeable. Please resolve the merge conflicts.

[jdm]

Looking better!
-S-awaiting-review +S-needs-code-changes

---

Reviewed 3 of 3 files at r1, 3 of 3 files at r2.
Review status: all files reviewed at latest revision, 3 unresolved discussions, some commit checks failed.

---

^{components/net/fetch/request.rs, line 152 [r2] (raw file):}
If we make this method take self by value, we shouldn't need this clone.

---

^{components/net/fetch/request.rs, line 153 [r2] (raw file):}
format!("fech for {:?}", self.url.serialize())

---

^{components/net_traits/lib.rs, line 167 [r1] (raw file):}
I'd go with:

/// Interface for observing the final response for an asynchronous fetch operation.

---

Comments from the review on Reviewable.io

[jdm]

Great! Let's squash all these commits and then merge them :)
-S-needs-rebase -S-awaiting-review +S-needs-squash

---

Reviewed 3 of 3 files at r3, 2 of 2 files at r4, 2 of 2 files at r5.
Review status: all files reviewed at latest revision, all discussions resolved, all commit checks successful.

---

Comments from the review on Reviewable.io

[KiChjang]

Just one sec, currently it doesn't compile and it generates this error:

servo/components/net/fetch/request.rs:153:9: 153:20 error: the trait `core::marker::Send` is not implemented for the type `fetch::cors_cache::CORSCache + 'static` [E0277]
servo/components/net/fetch/request.rs:153         spawn_named(format!("fetch for {:?}", self.url.serialize()), move || {

and goes on to say that fetch::cors_cache::CORSCache + 'static' cannot be sent between threads safely. Not sure what the best way to fix this.

[jdm]

https://github.com/servo/servo/pull/7275/files#diff-4039fbc0ced622014645f0d0d9c4e443R117 will need to be Box<CORSCache + Send> instead, I believe.

[KiChjang]

Squashed and fixed build errors. Little guy should be ready to merge, apologies for taking so long to finish this simple task.

[jdm]

@bors-servo: r+
No worries! Thanks for doing this!

[bors-servo]

📌 Commit ecf02a3 has been approved by jdm

[bors-servo]

⌛ Testing commit ecf02a3 with merge 0fc9410...

[bors-servo]

☀️ Test successful - android, gonk, linux-dev, linux-rel, mac-dev-ref-unit, mac-rel-css, mac-rel-wpt