move augmentClass definition above SyntheticEvent Proxy replacement

[walrusfruitcake]

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[aweary]

The browser mentioned in #10010 is QTWebkit, which appears to be an unofficial fork of Webkit. While this change is trivial, I'm hesitant to include changes meant to address dev-only issues in unsupported browsers.

The usage of Proxy here appears to be correct, which indicates that the Proxy implementation GTWebkit is using is possibly incorrect (especially since this Proxy call has been working in Webkit browsers for a long time).

[gaearon]

We could get it in but there's no guarantee we won't break again.

[aweary]

@gaearon do you want to make the call here? It's a (seemingly) innocent change, but I'm hesitant to accept since it sets a precedence for including changes for unsupported environments. But it's up to you.

[gaearon]

If it doesn't break anything I'm cool with taking it.

[aweary]

Cool, I'll verify everything looks OK locally and merge if so

[gaearon]

Seems fine to me, I'll get it in.