Using Shadow Dom CSS Animations on distributed (i.e., light dom) nodes with Polymer.dart
I believe @keyframes, like @font-face, have to be in document level CSS so you'll need to pull them out of your element. Here's an example: http://jsbin.com/zisupu/6/edit
Previously this was documented in the Polymer docs but has since been commented out. I've opened a thread to see if we can sort out a recommendation. https://github.com/Polymer/docs/issues/434
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Opened Chromium bug #382498