Intent to ship: Visual Viewport API on Android

Hi everyone! I would like to ship the Visual Viewport API [1] on Android. The initial implementation [2] was done in Firefox 63 behind the pref "dom.visualviewport.enabled" (see "Intent to Implement" thread [3]). It has since seen bug fixes, polish, and expanded test coverage. I intend to ship

Intent to Implement and Ship: CSSStyleSheet.rules, CSSStyleSheet.removeRule, CSSStyleSheet.addRule

Summary: Implement and spec some non-standard CSSOM APIs to converge with every other browser, since they're unlikely to ever remove their implementations and the lack of them causes compat issues for us, see the bug, the CSSWG issue [1] and everything cross-linked from there. Bug:

Changes to autoland repository configuration

If you don’t pull from the autoland repository, you can stop reading. The autoland repository has a “special” configuration: Until its changesets are merged into mozilla-central, they are in the mercurial ‘draft’ phase[1][2]. On Thursday May 9, 2019 we will change the repository to be configured