Fix a bunch of clippy lints
This fixes about 130 clippy lints. Let me know if i should split up the commit.
I wasn't sure about some of the changes, especially map_or instead of map(...).unwrap_or(...) and if let instead of single arm match were not always a strict improvement in my opinion, but i'll leave that decision to the reviewer :)
There are about 150 lints left which i thought were clippy bugs or i didn't know how to fix.
cc @Manishearth
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Enabled use of FontFamily enum type
https://github.com/servo/servo/issues/8371
In addition to replacing loose strings with the FontFamily enum in `font_cache_task.rs`, I also centralized the add_generic_font calls into one single function. If centralizing into one function is not desired or if anything else needs to be changed, please let me know.
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This patch does a number of things, unfortunately all at once:
* Hoists a large subset of the layout wrapper functionality into the style system.
* Merges TElementAttributes into the newly-created TElement.
* Reorganizes LayoutData by style vs layout, and removes LayoutDataShared.
* Simplifies the API for borrowing style/layout data.
There's still more to do to make the style system usable standalone, but
this is a good start.
Add test to constellation to avoid writing reftest image if there are pending frames.
This changes several tests that contain <iframe></iframe> from FAIL to TIMEOUT. This is correct
since there is a bug that prevents these iframes from ever rendering.
~~~There are also a few previous FAILs that changed to OK. These may be intermittents or they
may genuinely be fixed by this change.~~~
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Also change when pipelines become active.
This makes the constellation activate a pipeline as the current frame
when it is ready to do initial reflow, rather than when it is ready
to paint.
This fixes a number of intermittent failures that could previously occur
if an iframe was not visible - which would mean it was never moved from
a pending frame in the constellation to an active frame.
(It happens that webrender exposes these intermittents as permanent failures).
On http://en.wikipedia.org/wiki/Spotted_hyena, I was seeing a 100% miss
rate in the first fast cache lookup and 45% of total layout time in this
function. After making this change, the first cache lookup almost always
succeeds, and the time spent in this function drops to 8%.
Updated string_cache, html5ever, xml5ever and selectors in Cargo.toml files and Cargo.lock.
Removed references to string_cache_plugin.
Import atom! and ns! from string_cache.
Replaced ns!("") by ns!().
Replaced ns!(XML) and co by ns!(xml) and co.
Replaced atom!(foo) by atom!("foo").
Replaced Atom::from_slice by Atom::from.
Replaced atom.as_slice() by &*atom.
