Regarding css-properties.js, would you take a look at https://github.com/brettz9/jml/blob/master/shims/CSSStyleDeclaration.js and let me know if that content interests you in some manner? I added some more methods to CSSStyleDeclaration such as getPropertyPriority() and adding more type checking and conversions.

Note there are a few dependencies:

1. One is a shim for DOMException (e.g., my fork of @inexorabletash 's copy is at https://github.com/brettz9/jml/blob/master/shims/DOMException.js which indicates it also depends on shims for Object.keys and Array.prototype.forEach as also found in https://github.com/brettz9/jml/tree/master/shims ) which adds a convenience method DOMException.create() since the real DOMException does not allow itself to be instantiation through "new DOMException". Although I'm normally not a fan of adding non-standard properties (even if on a namespace), I think this one is unobtrusive enough and more convenient than packing all the code into each file that uses it.
2. Object.defineProperty as shimmed by https://github.com/eligrey/Xccessors/blob/master/xccessors-standard.js