layout: Remove `FontStyle` in favor of using the font style struct
directly, and optimize `get_layout_font_group()` to use a small vector.

Seems to be a 38% layout win on a site I tested with a lot of text.
Remove unused implementation of MonoCache
Move jsstring_to_str and jsid_to_str to conversions.rs.

This appears to be a more sensible location for them.

Relevant to #433.
auto merge of #3698 : ema-fox/servo/remove-monocache, r=jdm
auto merge of #3699 : Ms2ger/servo/jsstring_to_str, r=jdm

This appears to be a more sensible location for them.

Relevant to #433.
Update test expectations

The hubbub bindings set document.characterSet but we don't use it for anything.
html5ever doesn't parse charsets from <meta> tags yet, and I'd rather add that
as part of adding actual support for other encodings (which Servo never had
with hubbub).

Switching to html5ever also changes attribute parsing slightly (bringing it in
line with the current spec) and this breaks some of the <img srcset> tests.  We
don't support this feature at all.

Some other things change due to bugs in hubbub not present in html5ever.
Use html5ever for HTML parsing
Add a reftest for #1324

Closes #1324, fixed by html5ever.
auto merge of #3670 : kmcallister/servo/h5e-take2, r=jdm

r? @Ms2ger, @jdm

The parser is now a JS-managed object and we use hooks in html5ever to trace its internal state.  This should be memory-safe even if arbitrary JavaScript can run during a parse.  Please let me know if you think of a reason it wouldn't be!

I think the likely outcome of a garbage collection during parsing is a dynamic `RefCell` borrow failure, but I'm going to look into that after this lands.  It should be safe to trace the parser while it's mutably borrowed, as long as it's not shared between threads, so we can probably switch to `UnsafeCell`.
auto merge of #3697 : pcwalton/servo/get-layout-font-group, r=glennw

Seems to be a 38% layout win on a site I tested with a lot of text.

Other browser engines typically do not duplicate the information in the font style struct. `FontStyle` actually predates @SimonSapin's CSS selector matching library. It's time to get rid of it!

r? @glennw
Remove old hubbub HTML parsing code
auto merge of #3705 : mbrubeck/servo/rm-hubbub, r=kmcallister

Unused after #3702. r? @kmcallister
Update SHA1 for rust-mozjs. Also update the android Cargo.lock file for recent changes.
Make HTMLFormElementHelpers::submit take an enumerated argument instead of a boolean

Fixes #3677
auto merge of #3710 : gilles-leblanc/servo/issue-3677, r=jdm

...of a boolean

Fixes #3677
auto merge of #3709 : glennw/servo/update-mozjs, r=jdm
Update wptrunner to pick up crash-detection fixes.
auto merge of #3700 : Ms2ger/servo/update-wptrunner, r=jdm
Fix image_dynamic_remove reftest with incremental layout turned out

This also adds some extra debugging infrastructure which I found useful tracking
this bug down. A regression in the br reftests is also uncovered by this patch,
which I'll work on fixing next.

r? @pcwalton
Fixed the inline_element_border_a reftest with incremental layout turned on.