The Cascading Style Sheets (CSS) Working Group and Technical Architecture Group (TAG) have published four Working Drafts:

• CSS Typed OM Level 1: Converting CSSOM value strings into meaningfully typed JavaScript representations and back can incur a significant performance overhead. This specification exposes CSS values as typed JavaScript objects to facilitate their performant manipulation.
• CSS Properties and Values API Level 1: This CSS module defines an API for registering new CSS properties. Properties registered using this API are provided with a parse syntax that defines a type, inheritance behaviour, and an initial value.
• CSS Painting API Level 1: The paint stage of CSS is responsible for painting the background, content and highlight of a box based on that box’s geometry (as generated by the layout stage) and computed style. This specification describes an API which allows developers to paint a part of a box in response to geometry/computed style changes with an additional function.
• Worklets Level 1: This specification defines an API for running scripts in stages of the rendering pipeline independent of the main javascript execution environment.

The Web Performance Working Group has published a Group Note of Reporting API 1. This document defines a generic reporting framework which allows web developers to associate a set of named reporting endpoints with an origin. Various platform features (like Content Security Policy, Network Error Reporting, and others) will use these endpoints to deliver feature-specific reports in a consistent manner.