Fix loss of response type information in Fetch API
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Avoids mapping response types that are distinct according to [the spec](https://fetch.spec.whatwg.org/#concept-response-type) to fewer response types. Also updates test expectations to match that we now pass tests that check the response type.
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They're not at all related, besides both being asynchronous. This change adds
a little extra code in response_async(), but makes this code more readable
and reduces the unnecessary indirection.
This change also makes the build system slightly more parallel, by dropping
the dependency on bluetooth_traits from net_traits.
Also remove now-dead code that rustc warns about.
It turns out that we lost support for some of our custom URL schemes; I intend
to reimplement them, but I believe this will be significantly easier to do
once the legacy code is out of the way.
Update Rust to 1.14.0-nightly (7c69b0d5a 2016-11-01)
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- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [ ] These changes fix #__ (github issue number if applicable).
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- [ ] These changes do not require tests because _____
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