Make Attr::value private.
Simplify Element::set_attribute for its remaining callers.
Update layers submodule for AMD GPU fix.
Add rust-phf to servo build.
auto merge of #2647 : glennw/servo/issue-2462, r=metajack
Prepare makefile.backup for snashot changes
auto merge of #2648 : Manishearth/servo/makefile.backup, r=jdm
auto merge of #2644 : glennw/servo/add-phf, r=metajack
Don't fail on clearing nonexistant timeouts
Fix the assertion failure with inserting node contains child which has id into the document

https://github.com/mozilla/servo/issues/2630
auto merge of #2634 : saneyuki/servo/fix, r=Ms2ger

Fix: #2630
Implement support for parsed attributes.

This commit is heavily based on earlier work by Bruno Abinader in #2073.
auto merge of #2646 : Manishearth/servo/cleartimeout-opt, r=jdm
Implement Element.classList (partially fixes #1717).
Implement parsed 'unsigned long' attributes.

This commit is partially based on earlier work by Bruno Abinader in #2073.
auto merge of #2616 : Ms2ger/servo/attrvalue, r=jdm

Obsoletes #2073.
Make the conservertive stack scanner calculates `Temporary<T>` as root instead of calling root methods.

See: https://github.com/mozilla/servo/issues/2650
auto merge of #2652 : saneyuki/servo/root, r=jdm

fix #2650
Replace uses of JS<T>.unrooted() with JS::from_rooted #2580
Use Cell for Reflector::object.