The `offsetParent` is wrong in the `attached` callback

[notwaldorf]

on Chrome 43.0.2357.134 (Official Build) (64-bit), this code doesn't have an offsetParent. It works on FF and Safari:

https://gist.github.com/notwaldorf/44da856a3debdc8ab289

[sorvell]

This looks like a Chrome bug to me. I've filed:

https://code.google.com/p/chromium/issues/detail?id=516550

[sorvell]

After discussing this with some Blink engineers, it looks like fixing the bug will take a non-trivial amount of time. In the meantime, Polymer can use a slightly beefed up version of Polymer.ImportStatus.whenLoaded(cb) to defer calling attached slightly to avoid querying style/layout data too soon.