The spec was missing optional args that default to 0 for the following methods: skewX, skewY, rotateAxisAngle, translate The Spec IDL has been updated: https://compat.spec.whatwg.org/#webkitcssmatrix-interface

The following methods have been updated to match WebKit's behavior, taking optional arguments that default to 0: rotateAxisAngle() skewX() skewY() translate()

Thanks for the review!

Try looks good (some unrelated timeouts), will land when inbound is green.

Comment on attachment 8710795 [details] [diff] [review] Update WebKitCSSMatrix.idl to match latest spec updates. Approval Request Comment [Feature/regressing bug #]: Feature is Bug 717722. The known regressions are Bug 1241786 and Bug 1242333. When I wrote the spec I wasn't aware that web content depended on calling certain methods with default args -- sites broke and now we know. [User impact if declined]: Aurora/Dev Edition users will have a few high-profile broken sites. :( (Google Photos and Google Plus, probably more we don't know about) [Describe test coverage new/current, TreeHerder]: Try run in comments. [Risks and why]: Low risks. This change just adds default argument values to 4 WebKitCSSMatrix methods in the webidl. [String/UUID change made/needed]: None (no UUIDs are involved in webidl, right?)

Comment on attachment 8710795 [details] [diff] [review] Update WebKitCSSMatrix.idl to match latest spec updates. More web compat fixes, affects popular sites. Please uplift to aurora.