Implementation of #4432 adding `getPropertyPriority` to CSSStyleDeclaration. This is my first attempt at a Servo PR so I'm sure I've done something wrong. Let me know, and I'll fix it up.
As stated in #4432 tests for this are in #4085. If there are additional tests I can write now I would love to do that, I'm just not sure where or what those would be.
Source-Repo: https://github.com/servo/servo
Source-Revision: 7b7fe964d328362126a8a56ff463d48f3285391f
This does not implement any notion of CSSStyleDeclaration objects that do not have an owning element; there's no actual CSS object model in play here. This does support setting and getting properties of the style attribute for HTMLElement, and tries to implement the ambiguous CSS value serialization spec.
Source-Repo: https://github.com/servo/servo
Source-Revision: 824788649cd338c044d9396166af5b0f378d6685
