While editing work continues on the "second edition" of WebIDL here: http://heycam.github.io/webidl/, we have been fine-tuning the "Level 1" CR snapshot  to replace and supersede the 2012 version .
The "Level 1" editors are making final tweaks to the draft and tests, and hope to be ready to transition to Proposed Recommendation status by the end of July. The purpose of the "Level 1" document is to serve as a stable reference for W3C specs that link to WebIDL. It contains a subset of the WebIDL syntax that is considered stable (as verified by interoperable tests). Implementations should not use the Level 1 document as a guide, but instead track changes to the editors draft. We expect to follow-up Level 1 with a Level 2 as additional editor's draft syntax and behavior stabilizes, are implemented as part of other specs, and shown to be interoperable. -Travis & Yves  https://cdn.rawgit.com/ylafon/webidl/post-cr/l1-respec.html  http://www.w3.org/TR/WebIDL/