servo/servo — pull request #4190 by mttr (2014-12-03 01:43:55+00:00)
Title: Implements the :checked pseudo-class for inputs

Relevant spec:
https://html.spec.whatwg.org/multipage/scripting.html#selector-checked

Also modifies HTMLInputElement::SetChecked to no longer modify its
checked content value, instead making use of its internal checkedness
state now that we can match `:checked` properly.