Updating http_network_or_cache_fetch to better match the fetch API spec
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Actually, I think most of the functions in DOMTraversalContext deserve a nice
comment, but that's probably fine as a followup, I want to land the require-docs
thing now.
This is remminiscent of my recent @import refactor, and stayed there
incorrectly.
Note that it's the same code that lives in `update` (where it should live).
Update to rustc 1.16.0-nightly (4ecc85beb 2016-12-28)
<s>**This is not ready to land** since there is no corresponding Nightly build of Rust yet.</s> Update: we got a Nightly build on 2016-12-29: http://rusty-dash.com/nightlies
I made these changes to check that https://github.com/rust-lang/rust/pull/38566 fixes https://github.com/rust-lang/rust/issues/38535 (which it does, yay!) so I might as well publish them, we’ll need them soon enough.
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