Some IDL attributes appear on instances instead of on prototypes.
1. JSEvent properties on events ("clipboardData")
=> generated JSEvent::getOwnPropertySlot claims this is an instance's own property
2. HTMLDocument properties on document ("embeds", ...)
=> JSHTMLDocument::getOwnPropertySlot sets cacheable properties for JSHTMLDocument::info table entries
3. DOMWindow properties on window ("innerHeight", ...)
=> JSDOMWindow::getOwnPropertySlot sets cacheable properties for JSDOMWindow::info table entries
A side-effect of this, is that these properties do not have expected property descriptors. (They should have appropriate getters/setters and do not).
I think Chris fixed the majority of these. I'm updating Web Inspector now to better handle the changes we've seen. Lets close this out.