User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.11; rv:47.0) Gecko/20100101 Firefox/47.0 Build ID: 20160301030237 Steps to reproduce: Go to https://elements.polymer-project.org/elements/paper-menu-button?view=demo:demo/index.html. Click on the menu button. The dropdown does not work anymore. Actual results: The dropdowns don't work for any polymer component that contains it. https://elements.polymer-project.org/elements/paper-menu-button?view=demo:demo/index.html https://elements.polymer-project.org/elements/paper-menu-button Expected results: The dropdown should have opened.

Regression range: https://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=5e024441510f6d2b460e570d0e6d2dee0dc89723&tochange=1dbe350b57b17ec1ce2887441b79c6f51b429378 Brian Birtles — Bug 1239889 part 1 - Throw if the animation target does not have a current document; r=heycam Brian, I guess this behaviour is expected after your patch about animation target?

From console outputs: NotSupportedError: Animation with a target not bound to a document is not yet supported. b.newUnderlyingAnimationForKeyframeEffect() web-animations-next-lite.min.js:16 b.Animation.prototype._rebuildUnderlyingAnimation() web-animations-next-lite.min.js:15 b.Animation() web-animations-next-lite.min.js:15 b.AnimationTimeline.prototype._play() web-animations-next-lite.min.js:15 b.newUnderlyingAnimationForGroup() web-animations-next-lite.min.js:16 b.Animation.prototype._rebuildUnderlyingAnimation() web-animations-next-lite.min.js:15 b.Animation() I thought firstly the Polymer element uses a shadow DOM, but now we are using GetComposedDoc there[1]. Unfortunately the comment "Bug 1245748:..." was dropped though. So now I think the target element is associated with the document after KeyframeEffect constructor. [1] https://hg.mozilla.org/mozilla-central/rev/0de1790b3b8b#l1.77

This is actually bug 1245748. When our frame handling was implemented it relied on having a target element bound to a document. That caused problems when people started using Element.animate on elements that weren't in documents so we disabled that pattern temporarily in bug 1239889 which is the error produced here. I'm writing the proper fix in bug 1245748 but it's probably not going to land before the uplift so I think we'll just have to disable Element.animate in Firefox 47 (it will be disabled when it hits Beta anyway, but in order not to disrupt DevEdition we should probably disable it there too). I'll do that in bug 1247004.