At the moment, calling GetPropertyNames with the JSITER_OWNONLY flag *does* include inherited SHARED|PERMANENT properties. However, for operations like JSObject::sealOrFreeze(true), we don't want to mark prototypes' properties read-only. There should be a JSITER_OWNANDSHAREDPERMANENTONLY flag; all code passing JSITER_OWNONLY should be changed to use it. There should *then* be a JSITER_OWNONLY flag (underscore for consistency) that skips inherited SHARED|PERMANENT properties. Then, sealOrFreeze can be changed to use the latter.

Does this mean that properties being SHARED|PERMANENT now becomes non-transparent to the script? That might mean we have to stop using them in the DOM, if so (since I believe webidl currently calls for all DOM properties to be own properties...)

SHARED|PERMANENT has never been non-transparent to script -- make a DOM object a prototype of another object, then try hasOwnProperty("childNodes") or whatever on that object. This shared-permanent oddity will die soon, I very much hope for 2.x.