CERegistry.define use typeof instead instanceof

[cronon]

element definition may come from another realm or Function or Object globals may be sandboxed like in jsdom

original PR https://github.com/webcomponents/custom-elements/pull/180

fixes https://github.com/webcomponents/polyfills/issues/105

Reference Issue

[stale[bot]]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[cronon]

@stale, well the problem still exists here. Although if I'm not mistaken couple of months ago jsdom started to support Custom Elements by themselves

[stale[bot]]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.