showModalDialog in Chrome is always maximised

I'm trying to open non-maximised dialogs using showModalDialog, but in Chrome they are always opening maximised. Anyone have any ideas why? It is fine in Firefox.

I've put a working example on jsfiddle:

<a href="javascript:void 0;"
   onclick="showModalDialog('http://jsfiddle.net/');开发者_如何学Python">Go</a>

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It turns out that the problem was that I was launching Chrome with WindowStyle = ProcessWindowStyle.Maximised, and this was propagating to child windows. I changed it to WindowStyle = ProcessWindowStyle.Normal and cleared my Chromium user profile, and now it is fine.