allow createShadowRoot on body, fixes https://github.com/Polymer/polymer/issues/421
delete getDefaultComputedStyle from window

Looks like this was overlooked in https://github.com/Polymer/ShadowDOM/commit/864ca98, polyfill does not take affect in firefox without it.
don't discard destination insertion points of the shadow host itself when we rerender it. fixes https://github.com/Polymer/polymer/issues/512
Merge pull request #500 from jakemac53/patch-1

delete getDefaultComputedStyle from window
Merge pull request #502 from Polymer/polymer_512

don't discard destination insertion points of the shadow host
Merge pull request #496 from Polymer/polymer_issue_421

allow createShadowRoot on body
Re-land fix for unload/beforeunload events, fixes https://github.com/Polymer/platform/issues/83